drought tolerant

Politically Correct Plant Selection

A few years back a landscaper friend of mine sold his diesel work truck and bought a Prius. Even though the truck was more practical for his day to day work routine and actually got decent mileage, he'd been castigated by friends and clients for driving the "Beast" and felt the new hybrid would put a better polish on the image he was projecting. Coming back recently from three months of vacation, by all accounts his strategy seems to have worked.

Despite all the recently publicized problems Toyota has had recently, I like hybrids and the push to create more fuel efficient cars. During a period of the 70's that was dominated by enormous V8's, I was practically raised in the back of VW's that got triple their gas mileage. Kudos to my parents and to anyone today who wishes to conserve. What bothers me is the largely symbolic gestures businesses often make to ingratiate themselves to their customers.

I've done it myself, struggling with the symbolism of plant selection.

Here's the deal: Invasive species can have devastating effects on ecology and many invasive species were actually introduced for one reason or another. In the last twenty years I've seen the green industry become more careful in the growth and selection of plant material. Locally, for example, that means fewer Russian Olives (Elaeagnus angustifolia) are being planted. This a good thing given how the now ubiquitous invader has out-competed native species in riparian areas. But I see an unintended consequence to this elevated sense of concern: tough, drought tolerant plants are getting a bad rap in Boise because in much milder areas (e.g. San Jose, Ca) they tend to jump the fence. The truth is I've stopped using some plants in my installations not because I believe there is any danger in planting these blacklisted plants in Boise, but rather out of concern for the image I'm projecting.

I'm coming to grips with the inherent silliness of that reasoning. I finished a small commercial installation this week using, among other ornamental grasses, drifts of Nasella tenuissima. Mexican Feather Grass, as it's known by it's common name, is a wispy, somewhat ethereal grass that's the plant equivalent of mood music. It also happens to be a grass that some have called on to be banned because of its potential to become invasive. An attentive gardener employee at the location brought this to the attention of the owner and sent him a link to an online Sunset Magazine article about N. tenuissima (go here to read it). The author, Sharon Cahoon, does a great job presenting the debate, concluding that the matter of invasive potential needs to be determined regionally.

Honestly, I would be reluctant to plant N. tenuissima anywhere that receives more than 16 to 20 inches of annual rainfall but in our arid, high desert I think it's a fantastic alternative to many of the thirsty plants designers seem to use over and over (hey, I'm gonna start my own blacklist). While it's true it will self seed a little within a garden, in 20 years of digging in Boise's dirt I've never seen it wander into a neighbor's bed or naturalize into a non-irrigated area. I've heard the same debate about other plants like Euphorbia myrsinites, another tough, evergreen perennial. While I believe there should be a careful vetting process for any new introduction, designers should also be careful not to eliminate tough, drought tolerant plants from their design palette simply to appear, err, correct.

Native plants?

In the group of abused landscape terms, Native plants should file a restraining order against most of us in the green industry. In the parlance of our greenspeak, we stretch and deform the phrase like silly putty to make a point or to fit the sensibilities of our audience. It's particularly amusing to watch two green industry professionals use the term as a kind of litmus test, dodging and parrying like two strangers at a party discussing philosophy or religion. And just as terms such as "spirituality" and "solipsism" have largely been bleached of any specific meaning, the phrase Native plants has been assigned its own identity crisis.

I make this observation without any antipathy for the use of native plants in the landscape. In fact, using native plants is a fantastic way to reduce water, fertilizer and pesticide inputs. Plants that grow naturally in a geographic area are adapted to the ambient rainfall, soil type and zonal nuances of a specific region and generally don't need the life support system that makes up such a large percentage of our billable work in the green industry. But what is the criteria for defining a plant as being native? Is it a plant that once happily grew where your house now sits before all the top soil was scraped off and sold? A plant that's native to North America? Or is it a one gallon something or another at the grocery store that's marketed with a crossed out water drop and has a link to the Audubon society?

In the early 90's I worked as a wildland firefighter, initially on a hand crew and later as a first response helitack repeller in central Idaho. In the tiny window between the cooling ash of summer's fires and autumn's early mountain snowfall, we were given the job of preventing erosion in the recently burned areas. Massive sediment delivery into riparian areas can be devastating for fish habitat so our job was to cut down the burnt remains of trees and install them horizontally on the steep mountain slopes in an effort to temporarily mitigate erosion.

The longer term solution, re vegetation in these fire affected areas, is remarkably sophisticated and serves as an example of a particularly strict version of what Native plants means. Restoring an area to pre-fire condition means replanting with varieties that are as genetically as close as possible to the original plants. Calling a nursery in California and having two thousand one gallon Pinus contorta delivered to central Idaho is like wiping out all the Smiths in southwest Boise and replacing them with half the Smiths in South Bend, Indiana. There may be some distant relationship, but the unique qualities that defined the Smiths in Boise can't be replicated by the new comers. Broad genetic variation within a species is the first line of defense against extinction. Government agencies and private firms carefully collect seeds and propagate plants in an effort to maintain the unique genetic qualities of local, native plants.

Writing this, I'm looking out at our backyard and witnessing the beautiful collapse of the season. The gorgeous display of fall color from our very non-native trees peaked about a week and a half ago and I see the landscape slipping back into the monochromatic gray that defines our winter in southern Idaho. I try to imagine what our acre looked like before wagons began clunking down the Oregon trail a few miles away from our home. It's an image that's not too difficult to conjure as a short trip south will take you into an endless repeating motif of sage, bitterbrush and rabbitbrush. I'm not immune to the stark beauty of the high plains desert, but this natural landscape has a face that only a Minimalist, an ecologist or a chukar hunter can completely love. In all fairness, we're told this area was also covered in large clumping grasses before overgrazing, yet taken as a whole, I'm pretty sure that I don't want to return my backyard into jack rabbit habitat.

The truth is, in Boise our options are pretty limited if we try to adhere to a strict definition of what constitutes a native plant. Even the tough-as-nails Celtis occidentalis, one of Boise's few true native trees, can only be found in limited areas naturally where, in a convergence of botany and geology, large sandstone or granite boulders collect and concentrate water for the trees. We just have to face it: if the Amazon basin represents one of the most biodiverse places on Earth, we sit somewhere on the other side of the spectrum.

The arborist/science major side of me likes the idea of returning a piece of land back to its former condition, but the artist side stubbornly refuses to have his design options so cruelly curtailed. As is usually the case though, I think the answer lies outside of the argument. While two plant geeks might endlessly debate the relative merits of Chrysothamnus nauseosus (incidentally the most accurate scientific name for a plant) versus Ceanothus velutinus, the truth is that the true culprit in most landscape installation is turf grass. Planting most anything else will generally result in water savings and a decrease in the overall need for chemical input. I was once chided by a Horticulturalist friend for having a clump of bamboo (Phyllostachys mannii) next to our house in the front yard. I was compelled to point out that this particular clump of bamboo, known for its drought and cold hardiness, was surviving on very little supplemental irrigation; a point I couldn't make about the 1000 square foot swath of turf in front of the house.

In my own designs I tend to use a hybrid approach, using true local native plants intermingled with non-native, non-invasive & drought tolerant varieties. While there will always be a place for restoring original, native habit- driving through an average neighborhood I'm struck by just how much basic work still needs to be done to improve most landscape designs (enter token "sustainability" Meta tag here) . I've watched landscapers install turf against concrete on a south facing aspect and blame billbugs on the visible heat stress (and then charge the client for the chemical "solution"). The discussion of what constitutes a Native plant is largely academic in nature compared to the many obvious steps we can take to make today's landscapes less dependent on a constant life support system of fluid and chemicals.