Drought tolerance is an interesting topic. I’ve written on it before, but now have some additional thoughts to add, in part because we have recently moved to much more arid Central Oregon. A drought tolerant plant in Portland is a very different thing than one here where annual precipitation can vary from around 13″, very rare, down to as little as 5″, commonly 8″. While Oregon in general is considered to be a mediterranean type climate with dry summers and wetter winters, Redmond’s climate is strongly influenced by drier continental patterns. This last January, ’23, we received only 1/4″ of precipitation while Portland had 7.32″ about 120 miles to our northwest, on the ‘wet’ side of the Cascades. Drought tolerant then means different things in different regions and can vary widely within a region along with soil conditions, slope and aspect (which direction a site is oriented). Generally speaking, drought tolerance refers to the ability of a particular plant to endure periods in which available soil moisture is below that needed to support the plant’s metabolism. A tolerant plant can ‘bridge’ these naturally occurring ‘dry’ periods. An intolerant plant will suffer cellular, even structural damage and may be unable to flower and produce seed. Health is compromised should the drought last too long, resulting in internal physical damage and leaving it more subject to infection or infestation. A drought tolerant plant will have the capacity to respond in a healthy manner when soil moisture levels return to those that support active growth. Within these limits the stress it accrues does not compromise its health…beyond it though….Damage is accumulative. String a series of drought periods together and a plant’s capacity to recover is compromised. Because patterns of precipitation, of water storage and movement, vary widely across the earth, regions and sites have different plant communities associated with them. The condition of drought stress then varies with the location and the species. A drought tolerant plant on one site may crisp on another drier one. Of course this can work in the opposite sense as well, that a site may be too wet, but that’s another story. In the case of the PNW and many other regions, it is also the timing of the precipitation, when it occurs during a plant’s cycle of growth and dormancy. Continue reading
Category Archives: Maintenance
Controlling English Ivy and Clematis vitalba in the Landscape
I wrote the piece that follows while still a horticulturist working for Portland Parks about 20 years ago. It remains largely in its original form with a few additions, corrections and updates. Both plants are still under addressed in the landscape today. While employed I maintained my license as a public applicator of pesticides, a job requirement. I no longer have one, nor do I have a consultant’s license. In many cases herbicides can be an essential part of an effective strategy for the control of an established population of invasive plants. Invasive plants, like these, which are listed on your State’s Noxious Weed List, are there because of the the threat they pose to the environment and their capacity to infect and dominate a landscape, any landscape, across our region. In more than a few cases manual and mechanical methods of control alone are insufficient to ‘control’ the invasion and sole reliance on them will assure the failure of the establishment of a desirable landscape on a site. Herbicide use is thus justified. Large scale restoration projects are often dependent upon it. On a smaller residential property, with commitment and persistence, a homeowner may be successful, but even then they need to understand that there will be a continuing and significant threat of reinfection from surrounding properties, via birds carrying the fruit of Ivies and wind blown seed from Clematis. For some species, especially when the scale of the invasion and property are larger, its use may be essential. For many weeds this herbicide ‘threshold’ is very low before its use is a requirement. In this way scale works for homeowners as their properties and problems are smaller. Too often though properties are neglected and then the buyer inherits a serious problem. Using any herbicide will always have potential adverse effects on the environment, so if you choose to use it make sure you do so effectively. If you choose to use any of my herbicide suggestions, you are on your own. Do your research, understand your problem, to assure that your actions are effective, safe and responsible.
Getting Down to it: Your Viney Culprit is Probably Hedera hibernica, Irish Ivy, or More Rarely H. colchicum
English Ivy, a friend and co-worker announced early on in a then still continuing series of work meetings concerned with various issues of invasive plants, has been a kind of “anti-poster child” for those working in the regional conservation and restoration field. Its spread and control has been the subject of innumerable meetings, proposals and actions both fruitful and not. Eradication is no longer considered a realistic goal by many. The focus, rather, is on limiting its spread and control. Like other exotic invaders and introduced guests now run amok, from diseases to various shellfish and weeds, once a particularly well adapted species establishes a viable population base, it becomes a part of the disturbed novel landscape…it’s here and we’re going to have to figure out how to deal with it. This has always been the way of the world. The difference today is the rapidity with which these changes have been introduced through trade, the peripatetic travels of man (Man in the generic sense) and our never ending appetite for the consumption and disruption of land.
Agapanthus for the Maritime Pacific Northwest: Not all of these are well suited for us…or are they?
A fellow gardener asked the question about whether there were a list of sure thing Agapanthus, plants that a beginner could confidently choose and have success with in most of the maritime PNW. I’m going to say no. All of these are South African natives and while many of us can grow these in our gardens, because our conditions overall are marginal, a gardener is going to have to possess a good understanding of their site in particular and some knowledge of the cultivars that they are choosing. I’m going to borrow here from Manning and Goldblatt’s book, “The Color Encyclopedia of Cape Bulbs”, which discusses the bulbs of the Cape Floristic region and those adjacent areas spilling over into other parts of South Africa. Agapanthus species are native there, endemic in fact, occurring naturally no where else in the world. I’m also relying here on the SANBI website, the South African Natural Biodiversity Institute which has put together an incredible national program, which all countries should be building for their own countries. Being a South African plant aficionado I visit it frequently. To this I add my own observations and speculations, having grown several Agapanthus over the last 25+ years in Portland: These come from warm temperate and subtropical areas in South Africa, 10 species total, 3 limited to the Cape itself, all of which tend to occur in rocky grasslands. Other botanists have downgraded 3 of Manning and Goldblatt’s species and given them subspecies status recognizing only 7 species. Continue reading
Agave colorata and its Blooming Attempt in ’18
interest, their leaf color, substance and sculptural qualities, the margins of its broad, thick leaves, with their rhythmic rounded ripples, each tipped with a prominent ‘teat’ and spine. This is not a large plant, typically growing 23″- 47″ in diameter and my plan was always to keep it in a pot as it is from coastal areas of the Mexican state of Sonora, found sporadically in a narrow ‘band’ south into Sinaloa. Agave colorata is very rare and uncommon in nature and growing on steep slopes of the volcanic mountains in the coastal region in Sinaloan thornscrub. It often emerges from apparently solid rock cliffs sometimes clinging high above the water below.
Growing in Sonora and at Home
It is poorly adapted to our wet winter conditions though it is reputedly hardy into USDA zn 8, or as low as 10ºF. Its natural northern limit is thought not due to cold, but by excessive aridity in the northern parts of Sonora. I didn’t test it, leaving it outside under the porch roof, bringing it in when forecasts called for below 20ºF, as any plant is more susceptible to cold with its root zone subject to freezing. With perfect drainage and overhead protection, you might be able to get away with this in the ground, but the combination of significant wet with our cold is likely too much…still if someone wanted to try….At best I suspect this one would still suffer from fungal leaf diseases, disfiguring the foliage.
This is usually solitary, but it can be found occasionally in small clumps/colonies up to nearly 10′ across, pushing up against each other on their slowly growing and short ‘trunks’ to 4′ high. My plant produced just a few pups over the first third of its life.
Sonora has three distinct geographic areas all running along a ‘line’ from the northwest toward the southeast, the Gulf of California and its associated coastal landscape paralleling the Sierra Madre Occidental, sandwiching plains and rolling hills in the middle. The coast and plains/rolling hills are arid to semi-arid, desert and grasslands, while only the higher elevation of the easterly mountains receive enough rain to support more diverse and woody plant communities, scrub and Pine-Oak forests.
This region also varies north to south, the climate drying as you go north into the Sonoran Desert. Moving south on down into Sinaloa, and further, is the some what wetter ‘dry deciduous forest’ biome with an array of woody leugumes, including several Acacia. Agave colorata resides in the transition zone in between, in the portion of ‘thornscrub’ near the Sonoran/Sinaloan border. North and south the Thornscrub itself changes in composition. The Sinaloan Thornscrub serves as a transition zone between the desert and the slightly wetter, taller growing, Tropical Deciduous Forest that continues the south. All along this band running north on into Arizona’s Sonoran Desert are various columnar cactus a food source for Mexico’s migrating nectarivorous bat species. It is a unique flora community, containing species from bordering floral regions and other species unique or endemic to this transition zone itself. The area continues to be under threat, primarily by cattle ranching that moved into the region in the ’70’s and ’90’s bringing with it clearing and the introduction of non-native and invasive Bufflegrass, Pennisetum ciliare, also known under its syn. Cenchrus ciliaris, for pasture. Bufflegrass is also a serious problem north into Arizona. In Sonora many of the cleared woody species have since begun moving back in, while the smaller, more sensitive species have not. Climate change promises to further squeeze it. (The World Wildlife Fund maintains a website with good descriptions of many eco-regions I sometimes find it very helpful when trying to understand the conditions of a plant I’m less familiar with.)
When growing plants like this, one should keep in mind the concept of heat zones. The American Horticultural Society has created a map of the US delineating its ‘heat zones’. It is based on the average number of days an area experiences temperatures over 86ºF. At that temperature most plants begin to shut down their metabolic processes…they slow their growth. Check out the AHS map (AHS US Heat Zones pdf.) and keep in mind that we are warming up! The AHS map has us, Portland, OR, in zone 4, meaning we experience 14-30 days with highs over 86ºF each year. Last summer, ’18, we actually had a record 31 days over 90ºF! Now consider that the coastal/plains region of Sonora likely experiences between 180-210 such days! Agave colorata may not need this, but it is certainly adapted to such a level of heat stress. Something to think about, especially when you consider that we receive the bulk of our rain over the winter when our daily highs and lows average for Nov. 40º-53º, Dec. 35º-46º, Jan. 36º-47º, Feb. 36º-51º and Mar. 40º-57º…keeping in mind that we could freeze on most any of those dates. The Sonoran Desert receives its minimal rainfall in a summer/monsoonal pattern….This is why bringing such ‘low desert’ plants to the Pacific Northwest can add another degree or two of difficulty to your success!
Growing this in a pot made perfect sense to me, but every decision carries consequences, not all of which I anticipated. Most Agave don’t form a ‘trunk’ growing its leaves, in a tight spiral, crowded along a very abbreviated stem, which adds little to its length to separate each consecutive leaf., but Agave colorata adds a little ‘extra’ slightly separating its leaves, resulting in a weak and kind of puny stem. If you’ve ever shuffled pots containing Agave more than a few years old, you understand that their crown, their substantial top growth, is relatively heavy, A. colorata is no exception, in fact their leaves each seem more substantial than leaves on many other similarly sized Agave. This results in a plant that as it grows begins to lean over, eventually, laying flat across the ground. As a Monocot the stems of Agave don’t caliper up over the years as does wood. These have no cambial meristem which would add secondary growth, and diameter, to the stem and as I said, with its relatively massive and heavy crown, it leans. This is the same characteristic that gives their small colonies their height.
On Our Expulsion From the Garden: How Our Ideas of the Garden Shape What We Do
There are those who argue that life is short and violent, that we have nothing to look forward to other than our deaths…so we might as well grab for whatever we can now!….that is the path of the nihilist and the greedy, it serves as an excuse, a rationale for their choices, following an ethic of ‘why the hell not!’ This is consistent with the ‘beliefs’ of those who feel the weak get what they deserve, that anything that opposes their idea of dominance, is weakness and failure and they pursue it with the righteousness of a ‘true believer’. “Only the strong survive”. If our gardens can teach us anything it is instead that, ‘He/She who has the graciousness to take only what they need and gives back whatever they are able to, live on through the love and lives of those and that which they’ve nurtured, helped, befriended and mentored along the way and in this way have helped build a richer, more complex and diverse world.’ Our true legacy will be best expressed in the richness and health of the world we leave behind, of those that we’ve loved and taught. As competitive as the world is, it is this positive, cooperative, supportive aspect of life that makes it all possible. While the world is divided into heterotrophs and autotrophs, those that must consume to live and those able to grow and metabolize that which they need from the world around them, it requires them both, working in a balance to sustain them all. We humans, ultimately, cannot be any different if the world is to continue on. Continue reading
Winter 0f ’18 -’19: Cloudy, Mild With a Chance of….On Weather, Zones & Plants
It’s 41ºF at 5:30am on Mar. 12 as I begin to write this. We appear to have come out of the longest sustained ‘cold’ period of the winter of ’18-’19 which began on February 4 and continued through Mar. 11, a period of 36 days. Over those days we had freezing minimum temps at PDX, the official NOAA reporting station for the Portland area, on 26 of them. On two of those days, Feb. 6 and 7, PDX recorded the winter’s lowest temp, 23ºF, making it a zn 9a winter, mild for us historically and especially so for the temperate US as a whole, much of which was experiencing its own much colder temps. It’s mid-March and our high temps have climbed well above what they were and our forecasts call for milder, more ‘normal’ highs and lows now locally. It looks likely that not only are we going to be on the ‘warm side’ of normal, but that our lows have shifted into a pattern well out of the freezing range. (State ODF meteorologist, Pete Parsons, calls for a pattern of slightly warmer and drier weather than normal over March, April and May with the highest chance of this during May.)
While weather consists of moments, recorded data points, we attempt to make sense of it in its patterns over time…our experience of it. In this we are much like our plants. Plants too have their ‘expectations’ of the weather and those conditions that take them outside of them, outside their familiar patterns, the relatively quick changes and perturbations, as well as the longer sustained patterns, and extremes, are ‘noticed’ and make a difference. How does this winter compare? Continue reading
Our Gardens as Teachers
Of all the things our gardens do for us, arguably the most important is their role as our teachers, even in winter when a temperate garden ‘rests’, its surface crust or top few feet, frozen, maybe sheltered beneath the cover of snow, or, as ours so often are, simply too cold for active plant growth, the soil wet, the rain too heavy to percolate fast enough down through its layers, without the active aid of either the direct heating of the sun or its effect on plants, through evapotranspiration, pumping water back into the air as the plants grow. Gardens teach patience. They encourage us to become more careful observers…to think and plan, to anticipate and prepare, to understand that there is more going on here than we can readily see…and they teach us about faith and trust in the natural world, that there is always more going on than we can see. Continue reading
Roldana cristobalensis (formerly Senecio cristobalensis…now, Roldana petasitis var. cristobalensis)
Sometimes called Velvet Groundsel, this plant has been living and marketed under several different names. The first name in the heading is the one Jimi Blake ascribed to it, a name I didn’t recognize for a plant I’ve grown off and on in the past…it got lost in his list paired with a particular Thalictrum and I simply missed it…until recently. I knew it as Senecio cristobalensis and, had I recognized it, would have included it with an earlier post in which I focused on his favorite Asteraceae. I did actually mention the plant there simply as another Senecio that I’ve grown of value. Here I shall treat it more directly. The genus, Roldana, was recircumscribed in 2008 to include some 54 different species. Other authors include as few as 48 and as many as 64 in the genus, most of which used to belong to Senecio and are native to the extreme Southwestern US, Mexico and Central America. Most of the Roldana species are somewhat ‘shrubby’ herbs with a few, like this one woody, even tree like. Both genera are within the Asteraceae and share tribe status as well, Senecioneae. For the curious, Roldana spp., even more finely, are included in the sub-tribe, Tussilagininae, which includes the very commonly grown genus of garden plants…Ligularia! On closer examination the morphological similarities will begin to stand out to most of us. Check out all of the photos on the Wikimedia Commons page for Roldana petasitis. Roldana petasitis is the correct species name for this plant. With all of the shuffling and consequent confusion still going on in the world of taxonomy, especially in such a mixed large genera like Senecio, we must all be allowed our mistakes of nomenclature. It is a volatile changing world out there. Continue reading
The Lower Deschutes River: the Incursion of Invasive Plants and our Failure to Responsibly Maintain Native Plant Communities
[As I go over this post yet again, July 21, the 80,000 acre Substation Fire is still burning across canyon and wheat country here. Included in the blaze are the 20 miles of the Lower Deschutes canyon down to the campground at the confluence with the Columbia. Much of this burned down to within 2′ or 3′ of the riverbank including the historic Harris Ranch buildings. So, when you look at all of these pictures, with the exceptions of where the fire hopped and skipped, everything is charred. The Oregon Wildlife Federation, formed in the 1980’s to purchase and protect this portion of the canyon, has stepped up with $100,000 to help the area recover. It will take considerably more especially if there is any intention of making headway regarding the spreading invasives problem.]
[Now, another 2 weeks later more massive fires continue to burn across the dried up West that has just experienced another record breaking month of heat, while the president goes on ‘bleating’ and blaming it on our ‘bad’ environmental laws and all of the water we’re diverting into the ocean! ‘F’ing! moron!]
The last time we came here was eight years ago in December. My memory of then is much like the experience on this evening…only it was clear and cold. The light was similar except that then the low angled sun was due to winter, with that season’s urgency, not a late Spring evening like this outing. This time it is warm, camp is comfortable and nearby and the greens are still gathered around the river and the still moist draws and seeps. On that day we’d gone to Hood River for my birthday, to get out of town and there was a break in the weather so we drove here to these trails at the mouth of the Deschutes, hiked along the river, returning on the upper springs trail. Winter or summer, green only sticks around a little longer than we do, before it retreats…life is shier here, tough, but shy. The starkness of this landscape should be read as a warning to visitors, this is no easy Eden. Life is earned here or at least requires a strength, patience and frugality that many don’t have. This is much the same for people as it is for wildlife and plants. Them that don’t, can’t. That’s why it may be surprising to some that such a place has a problem with exotic invaders. What could possibly look on places such as this as ‘favored’? Well, Central Asia, especially its Steppe, with its continental, cold and dry climate containing many species that see such a place as this as home, or even better, without the competitors they faced back there. The temperature can swing widely here on any given day while the seasonal extremes can vary as much as 125ºF from high to low. Relatively few plants can thrive in this. The dry summers with their very limited and sporadic thunder showers, combined with the ‘wet’ winters, total only 10″-12″ or so of precipitation, plus or minus, is another major limiting factor. Of course, near the river, the moisture problem is moderated and a broader range of invasives can find a ‘foothold’. We, as a people, have ‘brought’ these weeds here with us in our travels, often as a result of our commerce. Those that have made it here are spreading. Too many prosper. Continue reading
Cottonwood Canyon on the John Day River: Place, Plants and Experience
Massive lava flows pushed around the lower John Day and Deschutes rivers over the course of several million years leaving them to find and carve new routes, often next to the very ‘plugs’ that filled their former canyons! Today, deep below the layers of hardened basalt that form the palisades and ramparts projecting out in tiers from the smooth full curves that rise above us, we look through 15 million years of accumulated history. The fine grained basalt shatters and fractures in line with their mineral structure under the forces of water, weather and gravity. Sagebrush and grasses dominate revealing an oddly ‘netted’ pattern across the sloping canyon hillsides, lit by the often harsh sunlight, illuminating some kind of subsurface movement of the thin soils that soften the slopes. The ‘net’ looks as if it had been draped across the land then stretched sideways catching and snagging on what lies beneath in a never the same, but consistent repeating pattern. It shows best when the angle of the sun comes across the pattern, not when it hits it head on or when clouds make it too diffuse. Coarse falls of shattered basalt spill down to the canyon’s bottom always seeking their angle of repose. The sagebrush steppe plant communities cover the surface and in their richness and vigor speak to the soils beneath. Along seeps and drainages cutting verticallly down the canyon’s face, spring lasts weeks longer, and species crowd in that you won’t see other than near the river. The surface botanical palette in this way reveals what lies beneath…if one knows what to look for. Cottonwood Canyon State Park is a great place to observe this. Continue reading