The Dry Garden: exotic trees that sip water

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The Dry Garden by Emily Green

The classic trees of California are big. Redwoods. Monterey pines. Valley oaks. So for those of us who live in cities but want a California native garden, where’s the giant sequoia supposed to fit?

My vote would be to tear down the house, but San Juan Capistrano nurseryman Mike Evans has a different idea. The man who for two decades has been a pillar of the native gardening community thinks that many Southern Californian homes with small gardens can be better off with exotic trees.

Evans, co-founder of the Tree of Life Nursery, is increasingly pointing his customers toward the leguminous trees of Mexico, Arizona and Texas. He’s even giving free classes how to use these trees, which are members of the pea family. “I am convinced that they’re perfect for patio situations,” he said in a recent class. “They don’t get too big. You’re talking about a wide range of plants that are diverse, easy to grow and that give back by flowering their heads off through the summer.”

To this he could add, hummingbirds love them. That’s the red Baja fairy duster shown here.

There are those who think that straying southeast of California state lines is a bad thing, a sin even. However, Evans argues not in terms of the political boundaries but of regional floristic provinces. To him, although the Sonoran classics of palo verde, ironwood and mesquite aren’t necessarily native, they can be better fit in Southern California than can conifers from the rainforests of Monterey or the oaks from the fog-cloaked dales of Marin County.

In common with many of our natives and their sister plants from Mediterranean climate zones around the world, these leguminous trees of the Sonoran tend to be nitrogen-fixing, meaning they absorb nitrogen from the air and sequester it in the soil. The ability allows them to thrive in poor soils, so don’t fertilize them. This is a particularly common trait among leguminous plants, so also expect pods from them.

The Sonoran natives being tested by Evans and then sold through these classes differ from California natives in one basic way. Their natural ranges lay at the confluence of desert and tropical climate zones, so they evolved getting winter rain as well as monsoonal summer showers. This means that they can adapt to a setting with some summer water.

Sometimes they can adapt too well. Arizona University cooperative extension warns against plants from genus Parkinsonia, known commonly as Mexican palo verde, on the grounds that it’s invasive. But if you fall in love with the graceful habit and showy yellow flowers, look for the hybrid called Desert Museum, above right, or simply hop around the leguminous family tree until you get to blue palo verde, which is from a different genus and species entirely (Cercidium floridum), below right. This looks so pretty year round that a crown of yellow blooms in early spring is pure gravy.

Of all these plants, the Baja fairy duster (Calliandra Californica, C. peninsularis), is increasingly being adopted in Los Angeles. It’s more of a shrub, but if 6 feet is as tall you want a patio tree, then all you need is a good pair of hand pruners.

One outlier among these largely feathery plants because of its shiny evergreen leaves and a definite contender for tree status is the 25-foot-tall is Texas mountain laurel (Sophora secundiflora). Texas horticulturist William Welch describes the wanton drop of spring flowers as “beautiful purple wisteria-like blooms smelling of grape Kool-Aid.”

From the genus of the most classic southwestern plant, mesquite, Evans is working with Prosopis glandulosa, or honey mesquite. Needless to say, but I will anyway, bees love it.

At Tree of Life, Evans has planted a desert fern (Lysiloma thornberi). Commonly called feather bush, this plant doesn’t need the puff ball white flowers it produces in spring his courtyard to explain why Evans chose it. Its fingered leaves are masters of sunlight. Rather than block it, they hold it in a dancing, luminous cloud — quite a feat amid the glare.

To track Evan’s workshops in gardening with leguminous trees of the Sonoran Desert and Baja, click to www.californianativeplants.com. Recommended reading: The Arizona-Sonora Desert Museum’s “A Natural History of the Sonoran Desert,” edited by Steven J. Phillips and Patricia Wentworth Comus for University of California Press.

Green’s column on drought-tolerant gardening appears weekly on this blog. She also blogs on water issues at www.chanceofrain.com.

Right: Baja fairy duster seed pod.

Credit for all photos: Christine Cotter / Los Angeles TimesIn case you missed it:

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