By David Cristiani
The use of accent plants, the Southwest green industry’s term for larger cactus and succulent plants, continues to increase beyond low desert communities. Some of that is more about following a trend, but some of that responds to the lasting benefits of a timeless fashion: reasons such as water conservation, desert wildlife habitat, and increasing visual interest or sense of place in our garden spaces.
Like another recent trend incorporating ornamental grasses, design principles also apply to accent plants, and many know that good design of plants popularizes their use. This is especially crucial with accent plants, not yet well-embraced in some locales.
My first step, as always, is to know the ecoregion where my project is located. (Editor’ note: The World Wildlife Federation defines an ecoregion as a “large unit of land or water containing a geographically distinct assemblage of species, natural communities, and environmental conditions.”) Then, it helps to choose design techniques and plants native there, or which easily adapt to, the realities of the site.
Soil types and climate will ultimately prevail, especially with maintenance capabilities or extremes of weather. This includes the range of temperatures that can happen over a few decades, and the averages.
Where I live and work, it’s the Chihuahuan Desert — arid, with a summer monsoon season and little rain or snow between October and June, but plenty of summer heat and periodic hard freezes throughout winter. Soils are alkaline and usually rocky or sandy, so all but small, specialized cacti of hillsides can be used anywhere except near lawns or low areas where water can pond during wet periods.
In heavier clay soils, it is wise not to use those or most other cacti and accents in low areas; however, such low areas are perfect for ornamental grasses, some shrubs, many trees, and a variety of wildflowers and perennial flowering plants.
This involves passive water harvesting, which is actually refining something required and ordinary — grading and drainage — and turning it into an asset, rather than it being a mere utility.
My recommendation is to first design the grades so water can drain into lower areas further from structures, with higher areas near buildings and walls for more visual interest — and using accent plants. Those higher areas can receive light drip irrigation, but will drain storm water during wet periods. Those can also create a place for accent plants, to draw attention from often more deciduous or ephemeral flowering plants during their dormant seasons.
The lower areas, which receive the most stormwater runoff, are ideal for low water-use trees. Those often create light shade but are unlikely to overshade accent plants, given their smaller stature. Such placement of those lower and wetter areas, along with higher and drier areas, is also related to where human traffic should and should not go.
STRUCTURE AND BONES
Depending on the design style preferred, as dictated by the architecture or the space, design principles need to be applied. Namely, good design is based on landscape appearances from important vantage points and the time of year. While milder coastal climates allow for much year-round interest, the desert is different: winter and summer are the dormant seasons in the desert southwest. Water does not always make up for extra heat and cannot help with extra cold, plus with the need to conserve water becoming a given, there’s a better way.
Use evergreen plants as the bones. Accent plants are able to perform visually in winter and summer, which many herbaceous perennials or deciduous shrubs with fall color simply cannot do.
Cactus, agaves and other accent plants, along with evergreen shrubs and low water-use trees, are the workhorses of the garden. Softening and further emphasis of such plants is performed especially well by their natural companions, low water-use herbaceous plants.
Wildflowers, perennials and groundcovers that mature at similar to lower heights than the accent plants they are used with, are a common choice. Many wildflower species recede in the colder and hotter months. If placed as a background to accents, they are unlikely to detract from the landscape in their off seasons, but instead, punctuate the space with a welcome burst of color and form. That, with less labor required to dead-head (which is quite unlikely with limited budgets of time or money). Such plants should be lower water-use, with an emphasis on native species, to bring in more native pollinators and create a local sense-of-place.
Not to be outdone, dryland ornamental bunch grasses also thrive in such spots. They mimic a common feature in wild desert grassland areas – yuccas and agaves punctuating masses of clumping low grasses, all equally hardy. For such grasses, consider all the more drought- and temperature-tolerant native grasses available in your area instead of non-native grasses.
Accent plants nicely draw attention to a space, even if few plants are used, or even more when used in mass. They make an even more ideal plant when they are safely placed out of traffic areas and/or used to direct traffic to certain areas.
When using accent plants, it is recommended that they are not designed for immediate impact, but for mature size. Plan for the plants’ ultimate visual impact. Crowding accent plants together in a young landscape can result in a snarled mass of spiny maintenance nightmares at maturity.
Create more visual interest and appeal for those newly embracing of our brand of desert daring.
David Cristiani is a landscape architect and owns Quercus, a solo design practice specializing in the planning of outdoor living spaces which are climate-adapted and regionally-inspired. Cristiani is registered in Texas, New Mexico and Nevada, now based in El Paso, TX. For more information, call 915.490.0065 email firstname.lastname@example.org or visit www.thequercusgroup.com.