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: Natural Areas
Fen, Bog and Swamp: A Short History of Peatland Destruction and Its Role in the Climate Crisis , a Review
Novelist Annie Proulx, begins her book with her childhood, giving us an idea of who she is, her attachments to the living world. She takes us with her on a walk she took with her mother as a young girl, through the neighborhood wilds, to an ignored patch of swampland. Her mother loved such places. She places her story in the larger story of the times of her birth and coming of age, of the 1930’s and the cruelties we perpetrated on each other and our limited view of the natural world, a world set as a table before us, for our consumption. She writes of her attachments to these abused and devalued wet landscapes, their necessity for a healthy natural world and what their loss means. Earlier, I reviewed Edward Struzik’s book “Swamplands”. Struzik has spent years working with researchers and conservationists in the field, and writing of his experiences. Proulx’s approach is much more personal as she works to place bogs, fens and swamps into a human, historical and cultural context. Continue reading
What Do We Do When the Whole World Feels Like its Falling to Pieces?
In this blog I focus on plants. Any gardener, botanist or horticulturist knows that plants, all living organisms, live in an incredibly complex, interwoven network of systems, each affecting the others, the health of anyone, in large part determined by the health of the ‘whole’. Life does not and cannot exist in a vacuum. We humans are also very much living organisms and subject to the same kind of limits as any species. What we build and produce, including those more abstract things like our social and economic systems upon which we are very much dependent, are subject to the same natural laws and limits, whether we recognize them or not. Very much a part of this is how we value other life collectively. Just because many may say other people and species are of less value, does not make this fact. The laws and ways of ‘man’ must remain within, and consistent with, the laws of nature. We are not at liberty to treat other life as expendable. We owe a debt and responsibility to all life. Life permits and supports us so it is incumbent upon us to do the same for it. Such is the natural law of reciprocity. Continue reading
Agave montana: Monte’s Flowering Attempt…and What’s Behind It
It’s October in Portland and my Agave montana is in the process of flowering…I know, we’re heading toward winter, with its rain and average low down into the mid-30’s with potentially sudden damaging temperature swings from mid-November into March dropping below freezing to the low twenties, with extremes some years, generally limited to the upper teens, though historically, some areas have dropped into the single digits, those Arctic blasts from the interior….Winter temps here can be extremely unsupportive of Agave’s from ‘low desert’ and tropical regions. Combined with these cool/cold temperatures are our seasonal reduction in daylight hours and its intensity (day length and angle of incidence varies much more widely here at 45º north) and the rain, ranging from 2.5″ to 6″+ each month here Nov.- Mar., resulting in a ‘trifecta’ of negative factors which can compromise an Agave, even when in its long rosette producing stage. Any Agave here requires thoughtful siting with special consideration for drainage, exposure and aspect. For an Agave, conditions common to the maritime Pacific Northwest are generally marginal, yet I am far from alone in my attempts to grow them here. Previously, in April of 2016 I had an Agave x ‘Sharkskin’ flower, a process that spanned the summer months, taking 7 until mid-October to produce ripe seed. I was initially a little pessimistic this time about A. montana’s prospects. Why, I wonder, if plants are driven to reproduce themselves would this one be starting the process now? 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.
A Course Correction: The Wild and the Human, On Repairing the Relationship Between Politics, Economics and the Environment
“We are the odd ones, with bright eyes, that see the wonder of a bountiful world. We don’t look through rose colored glasses…we’ve only removed the veil that breaks and blinds….Now, to cut the strings that tie us to the lie. ” Lance Wright, Jan. 2019
Gardeners are my people…well, actually, so are botanists, horticulturists, entomologists, ecologists, the weekend outdoor adventurers who in regular moments of awe, pause to take in the daily wonder of the world…anyone, really, who works with or has become enamored with the living natural world (and I’m going to include geologists too, at least those not taking their livelihood from resource extraction). I have a theory, that as our modern world becomes increasingly urbanized, and transformed by our use to that which supports urban living, more of us are becoming consciously aware of what we are losing, of the natural world that has been sacrificed, developed, along the way…and in ways, large and small, many, but still far too few of us, are choosing to make our lives reflect this understanding. We question the ‘stuff’ we have crowded our lives with, that ‘stuff’ we’ve spent our lives to procure while following the dream we’ve all been sold on. Many of us garden on whatever we have available to us whether it’s a quarter acre, a Juliet balcony or a kitchen counter space. We plant gardens for food or to support pollinators, to have something green and growing in our homes, we grow small succulents for their simple beauty, flowers for the vase or plants that provide cover and fruit for songbirds, there are many reasons…and we do this for the pleasure that it gives us, for the satisfaction that we are doing something to heal an increasingly ‘broken’ world. Yet the world continues to spiral down into more ugly chaos, in spite of our increasing awareness…it is not enough. I find myself drawn even more into the wonder and beauty of a single plant, the ‘miracle’ of life and the amazing complexity, the inter-relatedness of living communities…because, in spite of how our society views this planet and the countless organisms it routinely dismisses as secondary, and unnecessary or of little commercial value…life is in fact the center of meaning and value. Continue reading
The Carrizo Plain National Monument: Super-bloom 2019, our vacation early in the cycle
Why go visit the Carrizo Plain National Monument?…it is the last, significant, mostly intact, natural grass land in the state of California and puts on a floral performance that can be a showstopper when weather patterns produce sufficient rain over winter and early spring. This area was largely overlooked as the much larger Sacramento, San Joaquin and Salinas Valleys, also natural grasslands, attracted the interest of agriculture and settlers. The intensity and scale of agriculture in those valleys is mind-boggling, almost numbing. Today the big three support only small remnants of their former native biotic communities…much like the Willamette Valley here in Oregon…but Carrizo is different, largely because of its geology and elevation, two factors which strongly effected both the soils and weather, making it less attractive to agriculture and isolating it from markets. Continue reading
Death and Life in the Garden: Learning in the Garden Classroom
As gardeners our hands are ‘bloodied’ with the chlorophyll of plants…while it may not stain us as ‘murderers’, we are never the less complicit in their deaths…as much as we are necessary for their lives. Without us, as a group, these garden plants would never would have been propagated and, if not for our ‘selfish’ acts in the garden, choosing, designing and displaying them, many would be passing into obscurity, most of us knowing nothing of them or of their loss, their passages into decline and extinction, even more quiet, unnoticed, as too many already do today. While we may acquire and attempt to grow them with the ‘best’ of intention, eventually, they will all die, ill fit or not, suddenly or after many years in our gardens, as a result of our ignorance, impatience, simple curiosity, our desire for something ‘different’, or even in spite of our best informed efforts. Death comes to all things and our gardens are no exception. Our gardens art artificial after all, creations of our making and they do not comprise a viable population that will out live us, reproducing in place, making the adjustments that they must over time to survive. To do this would take an unprecedented amount of effort and coordination on our part and that of our neighbors. The setting of our gardens are unique to us and their purposes are much narrowed and more intentional than are the places their progenitors come from, the ‘gardens’ of their origination. For many of these plants our relationship with them might best be thought of as student to teacher as nature sacrifices itself in an attempt to teach us of what is being lost, ever since we stepped out of the loop that once put us in daily direct contact with nature and came to embrace this modern world and its expectations of consumption, ‘ease’ and never ceasing growth…so it is not ‘murder’, it is life, an attempt to return and reclaim. There is purpose to be found in our gardens, well beyond surface amusement and distraction in what is too often becoming an ever uglier world, or for some of us our need to impress in a game of one-upmanship. Nature demands more of us, that we accept our role as student and become careful observers, willing acolytes…maybe even crusaders….Too much? no, I don’t think so. 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
Growing and Understanding Globe Mallows in the Urbanized Maritime NW: Sphaeralcea spp. and Cultivars
Every plant evolved in and lives in context. They are dependent upon it for continuing support, not just for their survival, but for their well being as they grow, mature and attempt to reproduce. It is not just competition out there. Though we may order them from a catalog, grow them from carefully collected seed, receive them as gifts from a friend or purchase them from the shelves or rows at a garden center, they are individual plants, removed from their context…their futures’ will be short if we don’t make some attempt to recreate it.
Sphaeralcea are often called Globe Mallows and are another member of the large Mallow Family, the Malvaceae, some 244 genera with 4,225 known species. I’ve written recently of Anisodontea another genus of the family. Most of the 40-60 species of Sphaeralcea are North American natives of dry areas, growing from the Great Plains west and south into Mexico, with a few occurring in South America while a few others reaching into southern Canada. They include annuals, perennials and shrubby species, I’m looking here at perennials, all of which have very long bloom times, often spanning the entire summer into fall.
Sphaeralcea (ambigua) ‘Childerley’
Sphaeralcea ambigua, one of the largest growing species of the genus, at up to 3′-5′, often found considerably smaller, is native to the US Southwest, SW Utah, Nevada to Arizona and southern California down to Sonora and northern Baja, Mexico. They are found east of California’s Sierra Nevada and the several other smaller ranges of southern California, which shield them from moisture coming from the Pacific. It is the most xeriphytic of the genus, meaning, the most tolerant of drought. The USDA breaks the species into four separate subspecies, S.a. ssp. ambigua, the most commonly occurring form across the four states with the typical orangey flowers, S.a. ssp. monticola, the one occurring at higher elevations, beyond the Sonoran Desert and covering its Nevada range, S.a. ssp. rosacea which is limited to the San Diego area east to Maricopa county in Arizona, of the warmer Sonoran Desert, with a flower that is rosy-pink and S.a. ssp. rugosa which is limited to the Mojave Desert area with the more expected orange-red flowers. Both S.a. ssp. ambigua and S.a. ssp. monticola grow on north of the Mogollon Rim, an east-west running escarpment, the abrupt rise in elevation marking the southern edge of the Colorado Plateau. The other two subspecies grow below this and largely south and west of it. Continue reading