When we garden in the public view, and most of us do, at least where we front along the street, or even when we invite others into its more private and inner sanctum, and we grow plants successfully, people are going to ask you: ‘What’s that?’ ‘I didn’t know you could grow those here!’ and, ‘What did you do? they always die for me!’ In short, if you’re successful, people will regard you with respect and assign to you the attributes and position of ‘expert’…when all you did was try to follow the gardening maxim of ‘Right Plant, Right Place!’ In short, you tried not to kill it. Genuine expertise requires broader experience, study even, that the simple buying and planting of one particular plant cannot earn you. If you’re like me such easy success and adulation, can be embarrassing and often serves as a prompt, to look through books, search the internet and ask others, that you know who have way more practical growing experience than you yourself do, and gradually, the assignation of ‘expert’ feels a bit less flimsy, maybe even ‘earned’. I often tell gardening friends that I consider myself to be more of a dilettante, flitting from one plant or group of plants to the next. Inquisitiveness has always been a part of me and growing one Penstemon, one Banana or one Agave, never adequately ‘grounds’ me. Grow a few more and I feel a little more comfortable with it. Look into some of its ‘cousins’ and the particulars of where something grows, its climate and soils particularly, and I feel ‘better’, much like I did when I was preparing for mid-terms at school. And then I move on, my interest sated for the time being, somewhat comfortable in what I know and curious about the next group. Over time they all start forming a bigger picture out of what once seemed like a massive, unknowable puzzle and I enjoy solving puzzles. Having said this, I still don’t consider myself to be an expert, just an avid and focused gardener.
Take Agaves for instance, many professional botanists and horticulturists have focused most of their careers on this family, some limited to this genus. Me, I’ve grown a few is all, mostly in pots, but several in the ground here in winter wet Portland, Oregon (Our seasonal total in my neighborhood passed 50″ during this rain year, from Oct. 1 through April). There are 136 species, 25 subspecies, and 36 varieties (Gentry, 1982) and many more cultivars chosen generally for their vegetative characteristics. Currently, one of mine, an Agave x ‘Sharkskin’, that I purchased in a 1 gal pot over 15 years ago and have been growing in my front parking strip for around fourteen years, is undergoing the process of flowering, a singular event in the life of an Agave as a monocarpic plant, the mother plant dying after completing the process. Two things are notable about this ‘blessed’ event, one, there have been relatively few such flowering events of an Agave, any Agave, growing in the ground here in Portland, secondly, and anecdotally, very few people in Portland have successfully grown ‘Sharkskin’ in the ground, in Portland, for even a few years (Please contact me if you know otherwise and have photos or such a plant today.) How did I do this? First, let me back up a little.
To garden well requires several attributes, some of which are not normally associated with gardening, but if a gardener wants to grow, him or herself, I think are necessary. Most gardeners possess a given, base amount of wonder and awe at the green and growing world about them. It’s what opens their eyes to the living beauty and awakens a curiosity that I feel is absolutely essential to the act of gardening. Successful gardeners have developed their abilities to observe, they learn to see and question all of the things that promote and inhibit growth and they develop the ability to see subtle changes in performance and consciously wonder what may have caused them. They develop a particular tenacity or perseverance that drives them forward toward understanding, unwilling to simply assign an unexplained event to the magic of a green thumb or some inexplicable twist of fate. And with this they also learn patience. Things happen for a reason and the complexities involved in the living systems that comprise our gardens, our landscapes, are understandable. The survival and flowering of my Agave is only partly because of my particular knowledge and skills. It is not a ‘reward’ that I earned for putting in my hours. On a different, less amenable site, I could have labored the rest of my life unsuccessfully. Any plant has a range over which it can perform, beyond which, everything you do will be wasted. Still, you will be learning what ‘doesn’t ‘ work, which is often just as important as what does work. Failures round out your understanding. If a plant simply grows, if you are not challenged by some difficulty, what have you learned? Good gardeners kill plants…and they learn from such ‘mistakes’. We gardeners are part of the complex web of factors at play in our gardens. Our actions require just as much scrutiny as the physical conditions in our gardens. Wrong action can be every bit as fatal as a few more degrees of freeze, or of saturated soil or shade. While some authors have written of the importance of a gardener’s emotional state while tending it, it is the physical conditions, the biology of our landscapes that are absolutely critical to their survival and performance.
The Agaves I’ve Grown
[I’m going to add a little prologue here…a qualifier if you will. Years ago, at U of O, I read a book titled, If You Meet the Buddha on the Road, Kill Him’, it’s one of those ’70’s self-help books you don’t really have to read all of, the essence being in the title, and, that is that if you find people pressing their thoughts and beliefs on you, they are probably suspect and you should think twice before accepting them. Plant advice can be like this. There are the self-righteous among gardeners as there are in all walks of life. One person’s experience can be difficult to duplicate in another place. There are more variables involved in success, or failure, than most of us can enumerate. My experience growing Agaves, or any other plant, does not mean that yours will duplicate it. This posting merely presents my experience…as I remember it. Sometimes my actions were rash, impulsive, other times they were very thoughtful and considered. The value in any of this is only as a guide to help you when faced with growing the Agave that I discus here and, by extension, to urge you to ask yourself similar questions when trying these under different conditions. When planting any plant it is a good idea to ‘know’ your plant and the conditions that you are planting it into.]
There are many people more knowledgable of Agaves than I am, several local. People like plantsman, Sean Hogan, who was one time curator at the renowned UC Botanical Garden at Berkley and was responsible for the succulent collection. What I’m going to do is talk very specifically about my experience and ground it in what I’ve learned from others and books. Yes, there will be a certain amount of speculation when I address problems I’ve faced or have searched for explanations for my successes that have confused me as well. My intention is that it goes toward my own searching for understanding and improving my practice. It is an approach I attempt to carry with me through all of my gardening endeavors.
This is my first Agave. I still have it, or, rather, I have pups or offsets from my original mother plant. I got it at an HPSO sale over 15 years ago when it was still held at the Hillsboro County Fairgrounds, from a nursery called Trans-Pacific. It was this beautiful, but small, silvery blue sculptural piece. I knew almost nothing about these plants beyond their requirement for full sun and their dislike of winter wet. I was redoing the 60′ of my south facing parking \ hell-strip, it’s only 3 1/2′ wide, in a xeric theme and was planning to ‘match’ the already begun transformation of the 40′ to its east into which I’d already planted Nerium oleander ‘Double Yellow’ that I’d purchased from Plant Delights and a Callistemon viridiflorus that I’d gotten from Cistus Nursery. Most of the ‘new’ strip I was converting from a very weedy lawn that I’d never irrigated. The other portion of it had contained an immemorable melange that included an Othello Austin Rose, plants that never performed well suffering from their position and lack of consistent summer moisture. I didn’t want to have to commit to the watering regimen it required to assure performance, so I decided to go xeric, and chose this and several other members of the Agave family and other compatible plants for this planting, some of which I had not researched very well, whose requirements were not quite as xeric as I’d thought (For example, the ‘requirements’ of the mediterraneans I chose, which grow in summer dry regions, don’t quite align with many of the Agave that I’ve chosen since they come from winter dry regions that receive sporadic, though sometimes heavy, summer rains. Some mediterraneans are intolerant of summer rains/irrigation and may die.) A few choices I knew didn’t ‘belong’, like the Chinese Windmill Palms, from summer wet Asia, but they do very well here with little help once established and add to the aesthetic effect I wanted.
To prepare for planting I’d removed all of the plants and stripped off the remaining sod. I’d talked to Sean Hogan about soil mixes and chose his ‘Sean’s #1′ (40 percent sandy loam, 40 percent pumice and 20 percent well-rotted compost) that they mixed to order at Pro-Gro, a mix higher in pumice, lower in compost and bark than a typical garden mix. I removed the top 4″+ of topsoil with the sod/weeds’. This eliminated the growing weeds, much of the root, rhizome and stolons that could have quickly brought much of the worst right back and reduced the weed seed available on site for germination. It also gave me space to mix and build up my soil crowning the finished grade in a narrow bed. I hoped that this would be sufficient. Next I spaded the entire area coarsely leaving it rough, neither rototilling nor raking and breaking up the clumps to a uniform surface. Course is better, reducing the possibility of a ‘perched water table’ that can be created when the transition from one soil layer to another is too sudden and uniform. I layered my Sean’s #1 on top of this letting it sift down into irregularities I’d created. I ‘chopped’ this roughly in, again avoiding the rototiller that would uniformly mix the two. The entire center was crowned slightly, just a few inches, sloping down to the curb to the south and the sidewalk to the north. I worried that this was not ideal…that the soil depth and the grade of the site and crowned bed would probably not encourage surface runoff enough to make up for that. By sloping down, east to west, about 4′ across the 60′ of bed, drainage would be better than on a flat site, but like I said, not ideal, still, it’s what I’d done (Keep in mind that given the same soil conditions water will move down and away more quickly on this slope than on a flat site or one with less grade).
Another advantage gained from planting on a sloping site, especially in the winter wet northwest, is that you can ‘naturally’ tilt the crown of your Agave to match it. This aids with the issue of our winter rains, the tilt allowing the water to more easily drain away from the Agave’s crown and roots. Remember that Agaves come from arid and semi-arid regions where the rosette form of the plant can focus the infrequent rains to the crown and roots to take up the meager rainfall. Remember also that these grow in areas that when temperatures are low, slowing growth, there is little or no rain. Another one of their adaptations is their shallow, very efficient root system that is capable of quickly taking up the water from even a brief summer shower. In a region with a substantial six or seven month rainy cool winter season it is too much at the wrong time. Combine an Agave’s low water requirement during ‘cool’ seasons and it’s inability to ‘cope’ with the associated fungi and bacteria that occupy our winter wet soils and you have a recipe for Agave ‘disaster’. Draining away winter rains is vital to the survival of your Agave!
Another critical difference in soils is the naturally low soil fertility in the coarse mineral soils where these naturally occur. Higher fertility and readily available moisture combine to speed lush growth. This too in summer time can weaken these plants. They thrive on a certain amount of hardship. These are what botanists term, CAM plants, plants that utilize a two stage ‘pathway’ as they metabolize carbohydrates taking on CO2 at night and closing down its leaf stomata and photosynthesizing during daylight hours. (For more info on CAM refer to this earlier posting and scroll down to, ‘The C4 and CAM Photosynthetic Pathways’). Typical temperate region plants like those we are used to, utilize, primarily, the C3 pathway that requires much more water, most of which they lose out through their leaves to the atmosphere while pumping water and nutrients up from their roots (This water loss helps cool the surrounding air, a process that does not happen with CAM desert plants). Agaves don’t do this. They retain whatever they take up for their internal processes. Agaves grow slower than most temperate plants. They require less water and nutrient over a given period. What does this mean? Back off on the annual additions of compost. These don’t need it and will perform better without it. Our soils here are naturally too rich to begin with. Plus additional organic matter will increase your soil’s ability to hold water. Bad! Bad! Bad! Did I put down compost? Yes, unfortunately for several years I did. What would have been preferable would have been a 1/4-10 gravel mulch. My concern with the gravel mulch then and now is that in such a narrow bed much of it would end up in the street or down the sidewalk. This would have sped the drainage away from the crown and roots instead of held moisture there.
While spring planting this I also added Stachys byzantina ‘Primrose Heron’ and another ground cover, Origanum onites ‘Aureum’, with Euphorbia myrsinites. These would protect the soil, preventing surface compaction that normally occurs on bare soil here from rain and the erosion across the slope in addition to helping take up ‘extra’ moisture, keeping the Agave drier…I did think about this.
In the desert not every square inch of soil is occupied by vascular plants. Much of the surface often appears bare. Competition is fierce for available moisture. Desert soils are often naturally topped with a Biological Soil Crust, sometimes called a Cryptogamic Crust. This is composed of a highly specialized community of cyanobacteria, algae, mosses, and lichens…and the organic compounds they produce that bind the mineral soil particles together. They can compose up to 70% of the soil cover, all of the soil not covered by vascular plants. This ‘community of organisms’ creates a variable crust surface that swells and shrinks with available moisture. This crust can continue several inches down into the soil. These crusts primarily effect processes that occur at the land surface or soil-air interface. These include soil stability and erosion, atmospheric nitrogen-fixation, nutrient contributions to plants, soil-plant-water relations, infiltration, seedling germination, and plant growth. Here, bare, worked soils typically form a ‘hard’ crust after rain due to its ‘mechanical’ force, creating a surface that is more resistant to water infiltration. Bare soil here doesn’t fulfill the same functions that it does in an undisturbed desert environment with its crust intact. A living or gravel mulch is necessary for these plants here. These Biological Crusts do not form here and they cannot survive where there is regular disturbance of the surface. Plants and the organisms that comprise a healthy soil biota must serve the function of these ‘crusts’ here
While perusing Yucca Do’s on line catalog, an excellent source for desert plant material, I read their entry for this Agave species. They have quit offering this plant. Very hardy, they rate it at USDA zn 6b, but very susceptible to fungal infection particularly during cool wet periods!!! they write. This plant suffers damage for me nearly every winter in the ground, sometimes bad enough to kill the mother plant. (For those of you who don’t know I garden in zn 8a or b.) Interestingly though, it has always produced ‘pups’ or offsets in the ground and these survive. The rhizome reaches out shallowly from the mother plant, which has on occasion turned completely to mush, while the pups are sound suggesting that it is indeed the wet and not the cold that does this here (The wet penetrates and can saturate the upper soil levels even as the surface dries while our relatively mild winter temperatures do no freeze damage to the surface dwelling rhizome that produce the pups). I’ll then grow the pups for a couple of years and try one again someplace else. I currently have two, both surviving pups from the mother plant I had planted on my retaining wall and more in pots. The soil here has a fair amount of sand in it placed their during construction of the wall. There is also loose stacked broken concrete behind the wall typical of how ‘The Wall’ does their construction. Both of these suffered this winter with the much heavier than normal rain (50″ from Oct. 1 through April) The plants that I grow on in pots come through the winter without any fungal leaf spotting or rot. These generally stay outside the entire winter placed under a roof overhang, such as my front porch, where they get no rain. This is the case for several of the other Agave that I grow, keeping them dry during the winter allows them to reach their maximum cold hardiness.
I persist with growing this one because it is a very handsome plant when grown well with its ‘blue’ color, the imprint, the swollen teats (not my term but accurate in its suggestion of form) at the base of its marginal spines and the dark terminal spines themselves. Because it is not an overly large Agave, and the difficulty in growing it here in the ground, I guess I’ll have to get a nice pot for it occasionally up-potting it as it grows. Oh well!!!
I got this Agave when I was planning this same curb-side bed along with an A. colorata and A. parrasana. My records are incomplete here, but I think I got the three from Yuccado. This plant is a beast, my best performer in the ground, rarely showing any fungal leaf spot at all, never losing a leaf to it and being extremely durable in terms of physical damage. Physical damage, you ask, yes. With a bar across the street this plant and our A. ‘Sharkskin’ have both been bashed by car doors and I suspect kicked by pissed off boozers who’ve gotten ‘bit’, breaking terminal spines or causing a leaf here and there to fold and break. In spite of this damage I’ve rarely see any rot spreading from these breaks. This one wins the prize because one Sunday morning we got up to find this plant uprooted by a car and laying in the middle of the sidewalk with many of its leaves broken. Where the plant had been growing was a ‘hole’ formed by the front tire of the car that had jumped the curb to hit it!!! Of course it was gone with no note! Fortunately this happened in later Spring and the following days were warmish and dry. I left the plant sitting on top of the ground while the wounds air cured before spading the soil up and settling the damaged plant back in place. It sulked all of that summer, but grew normally the next. I was surprised it survived, but I shouldn’t have been given how they grow.
It’s age causes me to worry that this plant too will be flowering soon…and then dying as these are all monocarpic. Many Agave species reproduce vegetatively via bulbils, offsets on rhizomes or from leaf axils, each stemming from the plants meristematic tissue. Some species, like this one, depend completely upon seed for reproduction. A. montana doesn’t form clonal colonies around a mother plant that persevere after its death. A. montana is dependent on flowering and seed production to perpetuate itself. Bulbil production is limited to 17 species, (click here to read an article discussing how this happens on the species Agave murpheyii) forming little agave clones, high up on the towering inflorescence structure, rosettes, that live off the ‘body’ of the declining mother. These bulbils can ride high above for one, two years and sometimes longer until they separate or the flowering stem, the scape, is brought down to the ground. This plant will have to be replaced with a seedling.
For me this plant has proven to be very tolerant of our climate with our wet winters. Native high, to 9,000′, in Mexico’s Sierra Madre Orientale, this plant also has very good cold tolerance hardy to USDA zn 7, down to 0F.
Agave americana ‘Medio-Picta’
This is a particularly beautiful and distinctive architectural plant with the broad white bands running down the center ‘gutter’ of each leaf. The species and several varieties are used extensively around the world in tropical, sub-tropical and mediterranean climates sprawling on the ground or formalized in giant urn like pots. This is probably the smallest form. Several others can grow individual leaves over 6′ long creating an elegant and Dr. Seussian form. The inflorescences can by dominating at easily over 20′ tall. All Agaves tend to be dwarfed somewhat when kept in a pot and that’s what I’ve done with this one, well except for when I didn’t. I got mine years ago from Sean at Cistus. His suggestion was to keep it in a pot. Grown this way any Agave can be kept drier here improving its cold tolerance. It would seem likely that growing Agave in pots will yield plants that are less cold tolerant than one grown well in the ground. This is true for most plants as the entire root zone are exposed to the quickly changing air temperatures. In their book, the Irish’s assign this plant hardiness down to 15F. Many of my potted plants, like this one, spend the winter outside under the roof unless forecasts suggest lows will drop below 20F. Then I move them into my cool/lit basement for the duration of the coldest weather, then its back outside. My plant in the larger pot is a two person task when moving it. Because I have to move this down stairs for winter shelter we utilize a ‘pot-lifter’ strap system to keep the curved teeth away from us.
There are two things to remember when you grow Agave in pots: the soil mix for obvious drainage issues and the size of pot, for maybe less obvious ones. I have not lost any Agave in pots to over watering. I make my mix using 3 parts regular potting mix with 2 parts pumice and 1 part sand. This assures adequate drainage but provides enough of an organic component to hold some small amount of nutrient for healthy growth. Choosing your pot size is important because if it’s too large it will hold the roots in moist conditions that can be detrimental to the health of an Agave’s root system. The plant should not look ‘small’ in the pot. It should cover most of the surface when up-potting. Fertilization is necessary in pots, but these have much lower requirements than typical woody or herbaceous plants. I use about 1/2 the recommendation in spring of a delayed release pellet type. It is important to let the pot dry between waterings. I usually top water adding it until it starts coming out the drain hole. Sometimes I wait a little too long between waterings causing the soil mix to shrink away from the sides of the pot letting the water run through without adequately wetting the soil. In this case I set the pot in a tray with an inch or so of water letting the soil wick the water up, being careful not to leave the pot sitting longer than necessary. Sometimes this method is necessary as well when a plant is due for up-potting and physically covers the top surface making it very hard to top water. Because Agaves are very water efficient the soil drying for too long is not fatal, it only slows growth. If you wait too long the plants will start losing their turgidity causing the surface to ‘wrinkle’ slightly. They will quickly recharge upon watering. It is important as well to remember that all Agaves require some amount of water for them to grow well and they do this during the warmer months and their demand will be higher in pots. In the ground they will benefit from the occasional summer watering that will mimic the monsoonal summer thundershowers they evolved with.
Once my original plant produced pups and I had successfully potted them, I planted the mother out next to my front, south facing stairs, in the Spring. This soil is unamended Latourelle Loam, a rich fine textured soil common to much of the Willamette Valley that will open cracks when it dries. The slope is steep greatly increasing the drainage rate down through the profile as well as surface runoff. There was and still is a complete low ground cover to protect the soil surface, slow erosion and help draw off moisture through its growth. The plant grew well through the summer, wintered cleanly, though I don’t recall, nor do I have records of that winter and headed in to the next summer healthy. Then we came home one day and the plant was gone! a shallow hole in its stead. It had been a nice sized plant filling a 3 gal pot when I set it out.
Since then I have grown this only in a pot. (I now pin new plantings to the ground using three crossing bamboo stakes driven through the root ball when planting to make theft more difficult.) Every other year I pull my, now several years old pup out of its pot, cut away some of the circling rhizome removing any pups and potting them. I need to up pot it again, but have not found a pot yet that I like that’s 2″ or so larger in diameter.
This plant has beautiful and distinctive leaves with deep undulating ‘teats’ arranged across broadly curving leaves. Another blue almost glaucous white plant with deeply impressed leaves and very prominent dark terminal spines. I saw these growing in the Boyce Thompson Arboretum in Arizona in the ground in Spring of ’15. Their overall appearance is better in the ground as the heavy rosette is supported by the soil as the stems stretch and, because of this, are slightly more upright. It is a native of coastal Sonora, Mexico, but is reputed to be hardy down to 18F though some claim it is limited to zn 9. My plant is very heavy in its pot which stays more or less permanently on top of a 4-wheeled dolly so I can move it from under the roof protecting it from winter rain and radiant heat loss in winter. There’s no way we can get this up and down stairs to basement winter storage. I’ve also rolled it on the dolly into the house when we have had sustained periods with highs below freezing. This last winter, with our two, week long, cold snaps, this Agave spent the entire time outside.
The heavy rosette makes balancing and lifting this thing almost impossible. I did the repotting on the porch itself. I will not be up potting this plant again and will only water and fertilize it. Growers say this plant can start flowering at 15 years so I don’t think it will get too much bigger. When it does flower it’s 10′ scape, which is supposed to be a little floppy, will be a challenge to support.
I have so much time invested in this plant, that I’m too worried to set it out in the ground. I’d hate to lose it. This one is not thought to be especially tolerant of winter wet. I have another plant. I’m considering out planting, but haven’t decided where.
This species produces few offsets. Mine has been no exception to this. I’ve pulled 3 off of the mother over the years with one remaining attached to the horizontal stem on the mother plant. The largest of these is currently around 10″ across.
Agave gentryi ‘Jaws’
This plant has formed no pups in the four years that I’ve had it. I’ve been kind of waiting for this ‘blessed event’ before I plant it out. I’ve been contemplating removing my Yucca gloriosa ‘Tricolor’ that’s been growing in the parking strip in a position closest to the corner. This Yucca is tough, but it is very susceptible to fungal leaf spotting and even with regular ‘grooming’, removal of dead or nasty looking leaves, a task that is particularly hard on your hands and forearms poking you somewhere nearly every time you reach in, the plant has failed to live up to expectation for maybe more than 15 years. It may be time to pull the plug, place a large boulder to help ‘defend’ the corner and build up a mound to try this or another Agave on. This spot will get some shade from a thriving Trachycarpus fortunei which will also pump some of the excess water out of the soil, much like a larger Doug Fir or other evergreen conifer will do. I’ve utilized this recently when planting out a Puya venusta and a Dyckia ‘Red Devil’ in the ground near a Palms base elsewhere which, so far, has been successful.
Agave ‘Baccarat’ (a natural cross of A. gentryi x A. montana)
This is a gorgeous plant with an overall glaucous blue/white color, teeth and imprints that are reminiscent of cut crystal, at least for the plant explorers at Yucca Do who found it growing high in the Sierra Madre Orientale of Nuevo Leon. You’ll have to take my word for it because I have no picture of my now long dead plant. Its interesting that this ‘white’ plant is the progeny of two parents that are renowned for their rich green foliage as exhibited by the two that I grow. Both parent species share this region and this is thought to be a natural cross, and both species have proven to be relatively cold hardy which lead to my planting my small plant, acquired from Cistus Nursery, after growing it on in its pot for only a year, before it could pup. I was unaware at the time that neither parent formed clonal colonies. I chose to plant it in the curb bed planting it very close to where my A. harvardiana struggled, believing that this plant’s genetics would not only toughen it, but lead it to thrive! I was wrong. It perished its first winter, 2010. I intend to replace it. I still feel that this plant could do well here in the right place, in the ground. (As a note, I recently visited with friend and writer of ‘Danger Garden’, a lover of all plants pokey, about this and her experience with ‘Baccarat’ was very similar, though in northeast Portland her growing conditions are quite different having naturally better draining soil combined with slightly more extreme winter temperatures. Her site too was mostly flat planted in a slightly mounded position, mulched with 1/4-10 gravel.) This result was truly a surprise as I was relatively confident of my impending success. An interesting side note: in mid April I planted a Bulbine frutescens very near to the same spot….Remember all of that I rain I’d written of above, the hole that I dug was dry, so much so, that I filled it with water to perk down before planting this. I’d cut away Stachys b. ‘Primrose Heron’. I can’t imagine that it had pumped and transpired all of the water away, but where did it go??? An Asclepius speciosa has happily returned from the center of the bed where ‘Baccarat’ briefly resided.
Doing a little weather checking from October 1, 2009 through June 30, 2010 was interesting. This data is all from the Weather Warehouse for the downtown, KGW, reporting station, which is closer to my house in SE than the airport:
The month of October’s low was 39F, the mean 54.1F and precipitation 3.54″. November had a low of 35F, a mean temp of 45.3F and monthly precipitation of 7.39″. For December it was 18F, 37.9F and 4.99″. In January the numbers were 37F, 46.7F and 6.68″. February’s were 34F, 48.1F and 3.96″. March had a low of 35F, a mean of 49.1F and 5.62″. April had a mean of 51.0F and 3.99″. May was 55F and 4.63″. June 59.8F and 4.79″. The lows were all well above freezing for these last three months.
A few things jumped out at me as I compared these figures across the website’s table which covers the years from 1973 up through the previous month, first, the rain total, 45.59″. The annual average at KGW’s office is 35.98″, the winter in question was 9.61″ over, or a 27% ‘surplus’. The months above are when we receive the vast majority of our annual precipitation. June’s total was unusual being the highest since 1973. Sixteen of those Junes recorded an inch or less. Also notable over this month is that the mean temperature is significantly lower than the historical norm…only one previous June recorded a lower value and that was by only 0.4F. Historically this tends to run around 5F higher while last year’s mean for the month was almost 11F higher. Was ’09-’10 a La Nina year? These cooler than average means didn’t settle in until April. During the previous months the mean had varied higher and lower, but overall seems pretty average with a colder December ’09 standing out as well. What does all of this mean? I’m not sure, but I have to wonder that because these are arid region plants these periodic perturbations in amplitude of cool/wet days, is enough to push some of these plants, already near their limit, over the ‘edge’. Some area growers here go to considerable effort to construct ‘rain tents’ every fall. For these plants wet is what compromises them, as I stated earlier, significantly reducing there tolerance to cold. They might simply be saying, ‘Enough is enough!”
Something to keep in mind is that during these cooler winter months the evapotranspiration rate can be at or near zero. Gravity will be the only thing ‘drying out’ the soil as water slowly moves down through the profile. This makes an open porous soil texture all the more important to winter drainage. Temperate evergreens can be of aid here as they are adept at taking up water during this time of available soil moisture, their metabolic processes kick in whenever temperatures rise to within their range, something impossible in winter dormant and deciduous plants. This should be evident to any of you who have ever gardened under Doug Firs or other conifers. In an ‘open’ bed it will be just your Agave on its own…and the water. This example demonstrates that you may plan for the norm, but it can be those exceptional years that get you, or,in this case, get your Agave.
Agave (A. scabra x A. victoriae-reginae) ‘Sharkskin’
This plant has been a surprise from the beginning. I bought this at Dig Nursery on Vashon Island around 14 years ago. The first surprise was its identity, not knowing Agaves at all, it was labelled as A. parryi, which it is not, something I discovered shortly after getting it home and doing a little research. I had bought it because it was a handsome plant and for its purported cold hardiness. What it was though was a little harder to determine. Several people over the years offered the name ‘Sharkskin’ or ‘Sharkskin Shoes’. I let it slide as I had other priorities. I’d planted it in its present position 12 years ago, in the eastern portion of my parking strip an area that was planted before we moved in summer of ’89. This strip went through a couple early ‘transformations’ early on settling on a xeric theme including plants such as Callistemon viridiflorus, Ceanothus impressus ‘Vandenberg’, Nerium oleander ‘Double Yellow and Cistus x pulverulentus ‘Sunset’. I never amended the soil here to the extent that I did the western end of the strip and because when I planted this Agave, the other plants were well established and I did not want to risk pulling them out, I simply spaded up the immediate area chopping in a couple of inches of pumice careful not to create a water holding ‘tea cup’ effect. The resultant grade is crowned some 5 or 6″ above the sidewalk and curb, much higher and I would have started having more problems with soil or mulch spilling over. Its companions have changed over time including Linum lewisii, Zauscheria ‘Select Mattole’, a Penstemon pinifolius (that has succumbed to wet and compaction next to the sidewalk), a forgotten ground cover Sedum, Cistus ‘Grayswood Pink’ and Glaucium flavum, that got crowded out.
From the beginning this plant did well, in spite of the less than excellent drainage. In the first of April I planted a Bulbine frutescens ‘Tiny Tangerine’ within a couple of feet and was surprised at how ‘wet’ the soil was right here. I’d just planted two others, one at the western end of this section of the strip that was not and another further west in the Stachys that was surprisingly so dry that I filled the hole with water to let it soak in before I planted! Soils can vary tremendously. My experience with Agave and rot is that they are so susceptible that once compromised and infected, they usually succumb and do so rather quickly. Perhaps there is something in this one’s genetics???
This plant rarely ever suffered from even minor fungal spotting on its leaves. This last winter has been somewhat of an exception in that it has been very wet for Portland and this Agave responded with several of its older lower leaves succumbing to rot. I never covered it and it has no overhead protection from buildings or high canopies. It does have very good air circulation around it and no doubt benefits from the broad stretch of road asphalt to its south though I can’t see how that can help during our cool/wet winters.
This is an attractive and rather unique looking Agave as it shares attributes of its very different hybrid parents, its absence of marginal teeth, almost triangular in cross section leaves and its gray rough surface. It is a handsome plant with an almost perfectly uniform color and no imprinting in their surface giving them an almost manufactured appearance. This like my other larger Agave have growth that ‘sneaks’ up on you as their rosettes seemingly swelling adding leaves when you’re not looking, because they aren’t adding branches or significant height, at least until they start their final act of flowering propagating themselves. Having reached a diameter around 36″ it began to flower this Spring. I’ll be adding a post on this later on.
Agave lophantha univittata
This is one of my sad plant stories, not because it died, plants will do that, but because, after several years of care I dismissed this plant as too tender. I didn’t know its name and hadn’t bothered to figure it out. So, convinced of its tenderness and going through a ‘phase’ in which I thought I already had too many tender plants, I simply left it outside for the winter in its pot. I can’t tell you if it was abnormally cold or if I even left it out where it was rained on…shame on me. It had been a gift from Bruce Wakefield when I was probably gushing over the Agave and Cycads in his collection held in his greenhouse. He reached into the a pot and pulled off a pup handing it to me. Sorry Bruce! According to the Irish’s published table it is hardy down to 10F, if kept dry, of course I didn’t get the book until a few years later…such a waste! It comes from the Texas Rio Grande area and extends into the mountains south into Vera Cruz as high as 5,000′!
This is a striking plant with dark green foliage. Light green runs down the center vein creating a star like pattern when the rosette is viewed from above. Amazing when it form crowded colonies in the ground. There is a particularly nice form, A. l. ‘Quadricolor, which adds a lighter cream color to its margins and Yucca Do claims it hardy to zn8b! I will get it and this time be more attentive.
Agave ovatifolia ‘Vanzie’
Whale’s Tongue Agave, Agave ovatifolia is supposed to be one of the most tolerant choices for our climate, both the cool and wet, rated down to zn 7. I had not grown it myself and just missed out last year on Sean’s supply of ‘Frosty Blue’. I’m very curious about people’s experience with this here. Then last fall on a visit to the Ruth Bancroft Garden in Walnut Creek, CA, I saw several of their specimen, one of which is pictured above, in addition to a great many other amazing plants. I came back home and found this little guy at Cistus Nursery which I recently up potted. Planting out won’t be for a few years, but that is the plan.
Another collection from the mountains of Nuevo Leon, Mexico. One of the first plants brought back to Texas later bloomed and rewarded them with bulbils, one of the 17 or so species that will do this, of which one was sent to a lab where it was tissue cultured to quickly boost the numbers for the trade. These plants will also produce seed after flowering.
These make a large plant, their rosettes reaching 3′-4′ tall and 5′-6′ across.
Agave parryi var. parryi
If this Agave ever freezes out here, it will be the end of the world. -20F can’t happen here. This is the most tested/proven of the Agave here in Portland. ‘J.C. Raulston’ is a proven selection of this one. This does not mean that you can ignore drainage and grow it in the shade. No! This form is simply the most dependable. I’ll probably grow it on in a pot for awhile before I set it out. I grow several of my Agave specimen in glazed pots which don’t breathe as well and yes I do grow them in plastic while smaller. I violated the rule. If it is in plastic watering properly is that much more important. Let it dry out between waterings especially in cooler temperatures. Also don’t be in a hurry to put it into a larger pot. They hold more soil, and more moisture. Step up pot size gradually.
Agave parryi var. huachucensis
Hardy to 10F and briefly even colder if the plant is kept dry. I could kick myself on this one. I’m not a consistent record keeper and am evidence that one can break any habit. I did not record when I planted this one out or when I bought it from Cistus Nursery. My recollection is that I set it out the same year that I did the ‘Baccarat’, so in summer ’09. It was also in the ground when the A. p. var. truncata below died, demonstrating some additional toughness. It should also be noted that this is an amazingly ‘clean’ plant with little to not leaf spotting. I think that the few leaves it might lose annually around its base are more of a result of being crowded by the low Sedum pictured above which I tear out by the handful in spring close to the plant. It has added considerable size. Which ever the precise date of planting was, it was several years ago, and after the remodel, when I initially planted this bed with the Butia capitata just upslope in spring of ’08.
Agave parryi ‘Truncata’
This is a less hardy form than the type going down only to 15F according to the Irish’s, slightly less than the A. parryi var. huachucensis, corroborated by our own Sean Hogan. I planted this in my south facing retaining wall near to a Penstemon fruticosus var. scoulerii. It was perhaps a little too shady, but it is south facing, protected from any east winter winds and at the edge of the retaining wall about as well drained a site as I have without building a bed from scratch. It started to pup that first year in ’13 and then collapsed in the winter. It was a small plant. Late in that winter I pulled the remaining pup and potted it up, but all of my resuscitative efforts failed. It was a winter that began colder than normal, dropping in to the lower teens briefly in December, below the ascribed limit, drier too, having only one wetter than normal month, February, with over 7″. Did that one cold minimum do it in? Would it have survived were it a larger plant? Questions, questions.
It was never my intention to grow this plant in a pot long term. It is a large grower. I wanted it in the ground. This short steeply sloping bank on the south side of my house was created 8 years ago when we remodeled bumping the basement wall out to its position about 2 1/2′ back from the sidewalk (We could do this because we are zoned Commercial). It was the perfect time to have amended it with pumice, 1/4-10 (no fines) gravel or have brought in more os Sean’s #1, but I didn’t. I still could this Fall if I pull everything out. I thought this would drain well enough on its own given the slope, but I wonder if the house wall catches more rain coming up out of the south depositing it at the top then having it work its way down through the profile. Agave scabra, does very well in hot dry climates when some Agaves may need supplemental water in gardens under such conditions. This Agave, according to the Irish’s is more susceptible to rot and etiolation in cool damp conditions. Mine suffers in this way. While it has never died it has suffered most winters retarding and limiting its overall growth. This characteristic sensitivity does cause me to wonder if this bank isn’t as bad as I just suggested above, that it is the plant that suffers and might anywhere that I plant it. A good test would be to dig this and try it somewhere else and plant a different Agave in its place. That would be interesting. Where would I move it to? Mine is a mature garden, each addition or shuffle is going to mean a removal.
It is also interesting to me that this is one of the parents of ‘Sharkskin’ which has been very resistant to rot, leaf spotting or anything ‘bad’. Genetics and their sharing often results in individuals that can catch you completely off guard.
I’ve pulled a few pups off of this plant over the years swapped or gifted them to others. I’ve never heard how they’ve done out there or if they were kept in pots to grow into slightly smaller beasts.
Agave applanata (previously parryi) ‘Cream Spike’
This is a Japanese selection of a plant native to Vera Cruz, Mexico. It is beautiful with white/cream leaf margins and many very prominent reddish terminal spikes. Now I’m sad. I like this plant, a lot, when it’s grown well. Mine is not! I made two mistakes with this. I bought this is Spring of ’12 and the following year, when repotting it set it slightly low. It is important to keep the crown slightly above the soil whether in a pot or the ground, remembering that the plant may settle down slightly. The crown, from which the roots initiate, is very sensitive to moisture and damage, as are the plants of many genera. My plant sulked the following growing season adding very little growth with a couple of the older leaves rotting at their point of attachment. I left it and it spent another entire year status quo, the previous years result repeating. Finally, I pulled it out of the pot and reset it higher. This adjustment made all of the difference and it responded with strong growth. Then came my second, mistake.
When I bought this it was believed to be a selection of Agave parryi, one of the cold hardiest of the many species, though these vary from -20F to 15F. The first 3 winters, since this plant was struggling, I moved it to the lighted basement for the coldest period of the winter. This last winter though, secure in my hardiness expectations and the fact that I had a healthier plant coming into the winter, I left it outside, on the front porch, under the roof overhang where it stayed dry with most of my other Agave specimen and ‘babies’. It should have been fine. We had a significant cold snap with just freezing highs in early December, then it warmed into a normal range. Sometime after early January’s cold snap of several days below freezing, I noticed the tissue collapsing around the base of the outer leaves. I quickly moved it to the basement, but the damage was done. The outer leaves continued to decline, losing turgidity and blackening. I cleared the dead collapsed leaves away which were holding moisture and bacteria against and around the plant’s base. I kept this completely dry until mid-April after several days of far above normal high temperatures in the high ’80’s before bottom watering it, setting it in a tray, with a weaker liquid fertilizer solution. We shall see if it recovers or fails completely.
Agave potatorum (?) ‘Kissho Kan’
This is a zn 9 plant, that must be protected below 20F, again assuming you are keeping it relatively dry, otherwise even less, if you aren’t into living dangerously. I knew this going in with this plant when I bought it in June of ’11. I grew it in a pot with my regular xeric mix growing it on for a couple of years, slow and steady. This ultimately is a small plant (though the species is suppose to get quite large without the variegation of course) and I decided to plant it in a large shallow pot with several other succulents. The pot was cast concrete and the whole thing quite heavy. That following winter I kept it under roof to help keep it dry and when the cold hit hard, I decided not to carry it into the basement or up on to the concrete front porch. Instead I pushed it together with other pots under the back deck roof and threw a tarp over it. Turns out, it was not enough. It had been growing well, forming offsets, all of which suffered. I pulled them out of the group pot and potted three of them individually. Two survived, and grew well last summer, the third failed, too heavily damaged, died along with the mother. This last winter they spent in the basement under lights and look good, though they are still smaller than the original mother plant. Lesson learned.
Interestingly, this plant has proven to be less tolerant of intense summer sun for me than any of my other variegated Agaves. The whole plant kind of blanches. This response is more characteristic of many of the broadleaved evergreens and deciduous plants I’ve grown over the years including perennials and many of the conifers. It is often said that this is some kind of response to insufficient chlorophyll in these leaves, but I wonder because it is not always true. If a leaf is white, cream or gold, wouldn’t it naturally reflect more light away and be more resistant to such a reaction and burning? Some such plants have proven to be quite tolerant. I’ve wondered if some of these variegated plants also suffer from a thinning of the cuticle, the protective layer that covers a leaf’s epidermis. A question for later.
Agave angustifolia ‘Marginata’
This is an elegant and forgiving plant in that its terminal and marginal spines aren’t particularly aggressive, yes they will still poke you, but they won’t rend the flesh from your bones. This one was gifted to me two years ago and I’ve treated it like my others that can take a freeze, but if we’re going to ‘enjoy’ sustained cold, I’ve moved it to the basement for that period only. When shuttling plants back and forth I minimize the time spent under protection as I do not want to encourage growth which will effectively reduce its current cold tolerance having shifted its metabolism into a more active phase. This one was somewhere between ‘Kissho Kan’ and ‘Cream Spike’ in protection and it suffered not at all. I guess for this to mean much I should have recorded my moves and temperatures, but I have always done this more by ‘gut’ than science. My basic approach to all of these is to push it, to find out what they can take and not simply ‘color between the lines’. In any case, when I have a pup to ‘play’ with I’ll do some more serious testing.
Interestingly, if this plant ever does flower for me, it is one of the few that will form ‘bulbils’, little plants, high up in the inflorescence.
Agave victoriae-reginae ‘Porcupine’
I don’t know why it took me so long to grow one of these A. victoriae-reginae selections. Now considered in danger of extinction across its home range in Mexico north into Nuevo Leon, especially since it is hardy down to 10F and perhaps lower. The Irish’s suggest planting it on a mound in cooler-wetter areas. Its compact size generally around two feet in diameter or smaller, should make this a plant where space can be created/found for it. They make great pot specimen. The literature suggests that these produce offsets only occasionally and that in the wild they are generally found solitary rather than in clumps. A selection that is slow to offset this one is a little more difficult to produce truly for production and sale as seed grown plants will show some variation. As I mentioned before few species produce mini-plants in the form of bulbils when they flower. While a single plant can produce 200-300 and more bulbils they are only available at flowering which may take ten, twenty or more years, not exactly a system that can produce on demand. Some Agave, like the above mentioned A. ovatifolia ‘Vanzie’ are now being produced by tissue culture in labs making them much more readily and cheaply available than in even the recent past. I don’t know how common TC production is for the genus today.
Agave store much of their photosynthesized carbohydrate for later use when the plant begins to flower growing a relatively huge inflorescence or structure holding the individual flowers, an event that only happens once for each plant and can take as much as 20 and more years or as little as 9 for some species. They also store it in expanded root structures called rhizomes from which can grow the offsets or ‘pups’ that are clones of the mother plant. Some species form extensive and crowded colonies in this manner while others produce only occasional offsets, sometimes only in the early adult stages of their growth and others produce none at all. A. v.-r. does so only occasionally.
Agave utahensis var. erbospina
I got this from Burl at Rare Plant Research in Spring of ’14. I love the long papery spines. I repotted this last summer. This is a hardy tough plant to as cold -10F and is the most northern growing Agave. These are said to love heat and want exceptional drainage….ummm, I may just keep it as a pot plant. This shouldn’t be too hard as it is a small compact plant to 1 foot tall and 16″ across. This plant can live year round on your porch, in the sun under the roof. When it blooms it will reach 5′-8′ forming a spike, a raceme or a narrow panicle. I imagine in a pot it will need a bit of support to keep from toppling in a breeze, but should be fun. In the ground it can form large clumps so I’m sure there will be pups in my future.
This was a mail order plant in the Spring of ’06, so Yucca Do ??? Maybe? My record keeping has not been consistent from year to year. I don’t remember why I ordered it other than its hardiness down to 12F. I hadn’t ever seen a specimen before. Maybe it was its relatively spineless structure having very few tiny ones on the margins or its overall softness or flexibility, but this one, if happy, is large, up to 5′ tall and 10′ wide, I’m not sure what I was thinking…. It comes from the arid parts of Mexico and the SW US as a cultivated plant…it is not found in the wild. I remember planting it on the front bank near the A. scabra and having it die/rot back. I pulled at least one pup off of it. The winter of 2009 or ’10 caused this one to failed completely as it did my Agave x ‘Baccarat’ as described above. I never got too attached to this plant, it lacked some of the character of the others that I’ve grown and I simply don’t have the space for it. So, I’ve never considered replacing it.
Protecting My Potted Agaves
I have another temporary winter storage are beneath the shed roof above my back deck and yet another under my bamboo framed ‘Pagoda’ in the back of the garden. Each place provides a slightly different level of protection. Sometimes these outdoor areas are filled with more recently potted starts that I’m just trying to protect from radiant heat loss.
Agaves, Yuccas and Related Plants: A Gardener’s Guide, Mary & Gary Irish, Timber Press, 2000
Such a helpful article. I live in Tsawwassen British Columbia and want to grow Agaves in pots, unprotected from cold but completely protected from rain (covered by a deck). I am wondering if Agave Utahensis, Agave Parryi (standard form) and Agave Parryi ‘Truncata’ would survive in these conditions during one of our cold spells. Our Arctic events usually last a week to even two weeks where the temperature could range from as cold as 18f to 25f with daytime highs from 26f to 32f. If they plants were totally dry, would they survive unscathed?
Your winter temperature minimum range shouldn’t be a problem with these. Any of the A. parryi should be fine…and many others. Moving them under roof in winter will protect them from radiant heat loss, so it is better than exposed. Keeping them dry, top and soil, over the winter, assures that they will be their most cold hardy. Wet soil reduces cold tolerance. Use a well drained potting mix to plant them in. Agave are somewhat susceptible to damage from sustained freezing temperatures in pots. Remember that the earth’s mass protects roots from freezing too quickly, as frost penetrates deeper much more slowly into the earth than it does a pot exposed on all sides. There are many other species and cultivars that should work for you in terms of cold. I also grow A. montana, A. ‘Jaws’ and A. ‘Sharksin’ in the ground here. A. ovatifolia and its forms is reputedly one of the toughest and most dependable Agave for the NW. My A. americana forms often spend the entire winter outside under the roof. There are several very large A. salmiana var. ferox growing in the ground here, even flowering!..mine is still in a pot. Some report A. victoriae-reginae hardy into zn 7. Don’t be afraid to experiment. Also, check with local gardeners. I know that the Vancouver area has many gardeners who’ve been pushing the hardiness limits. Check with the gardeners in the NW Palm Society. Agave also require heat to properly mature. This might be a more limiting factor for you. I know gardeners on the Olympic Peninsula and in Victoria who are less successful with plants like Agave because of their heat requirement. Consider it an experiment. Be careful where you site them. A plant that goes into winter that has not had enough heat will have compromised cold tolerance. So in summer be sure to set your plants out where they can get maximum sun/warmth…and don’t forget to water during the summer growing months, that is when the need it. Some Mexican species may be listed as growing in part shade, but this is a recommendation for Sonoran and intense desert conditions. Keep records. Find your garden’s microsite that are more supportive and give it a try. Gardening is an experimental endeavor.
Excellent info in your response. In a nutshell I think:
– a lack of heat won’t be a problem because they get full sun most of the day and their covered location is almost always the hottest place in my yard. Not that they will have a preponderance of heat (I went to Palm Desert, CA this summer…I now realize what real heat is!) but they will receive much more heat than the average Victoria B.C. experience
– They would benefit from protection from the cold for at least this winter because they were just purchased and repotted. I will give them next summer to settle into their pots. So for this winter they will go into my crawl space (a heck of a good microclimate) during a cold event…and for next winter I will throw blankets on them and put them up against the wall during a cold event…then maybe the third winter I’ll leave them unprotected. And I won’t water them in the winter unless the leaves start to show evidence of water deprivation.
– And you are right, I should experiment, and I will! Well, as soon as I can easily buy some other species. not super easy to do around here. Although Phoenix Perennials in Richmond is great!
If I ever get to a place with enough light to experiment more with Agaves, I will start by referencing my learning here. Happy to report though, that the little A. americana ‘Medio-picta’ I got from you last year survived the winter outside! Hooray!
Fabulous article Lance! And heck I am blushing at the mention…however I must take exception to the idea that I’ve got well draining soil. It’s clay and it’s horrid. There are 2 spots in my garden where the soil is mysteriously well draining, both sadly unsuitable for Agaves.
Your mention of A. ‘Kissho Kan’ being less tolerant of sun had me nodding in agreement, it’s a wimp! Although I guess it is nice to have an Agave that prefers a bit of shade.
Also, for what it’s worth, my brother in Phoenix has experienced significant damage on his Agave angustifolia ‘Marginata’ with a high-20’s freeze event. I think the Irish’s claim is a bit optimistic.
Happy to see you’ve got an A. Ovatifolia…mine are doing fabulous!