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The Dry Garden: Watering native plants in summer -- or not

June 23, 2009 |  7:42 pm

BuckwheatNow that so many Californians have heard the garden gospel and made native plants their religion, how can they keep flowers like California buckwheat, above, alive long enough to see another spring?  The problem, Emily Green says, often isn't a lack of water. It's too much. For more details in the latest installment of our low-water gardening column, read on.

-- Craig Nakano

Photo: Los Angeles Times 

By Emily Green

While most Southern Californian gardens require more water in summer, native gardens need less. In fact, they take so much less that if you haven’t watered a native plant to death, then you probably haven’t tried native gardening. It’s a rite of passage, closely followed by the second rite of withholding all summer water -- and killing the plant that way.

This is not to suggest that native plants are hard to grow. They’re just easy to kill. The key to reaping their beauty and benefits without watering them to death is understanding summer dormancy.

This switch from spring growth to summer sleep is happening now. Formerly succulent inner leaves of the sages are turning yellow, even purple, then dropping as a new set of smaller, tougher leaves gird for summer. A similar wash of yellows is appearing in the inner leaves of the normally deep green foliage of the native lilacs.

For those new to California, the onset of summer dormancy feels familiar. It’s faintly melancholic, like the transition from fall to winter back East. Except that in the temperate coastal plains and foothills of Southern California, plants hunker down in advance of the heat and dryness of summer.

Once a native gardener becomes attuned to the onset of dormancy, the challenge becomes whether or not to water. There are different schools of thought on this, so I took a straw poll among a trio of experts: Bart O’Brien, special projects director at Rancho Santa Ana Botanic Garden in Claremont; Mike Evans, founder of the Tree of Life Nursery in San Juan Capistrano; and city of Santa Monica native gardening consultant Susanne Jett. The consensus: Many (but not all) natives should be judiciously watered in the summer, slowly and deeply, once or twice a month.

The reason, says O’Brien, is that popular garden cultivars have frequently been bred from species that are native to cooler parts of the state. For Evans, one of the benefits of these cultivars is that, grown with modest irrigation, they don’t become as haggard in the mean season as their wild progenitors.

Determining when and how much to water requires knowledge of your plants, soil and climate zone. Two of the best organizations designed to help are Rancho Santa Ana and the Theodore Payne Foundation for Wildflowers and Native Plants in Sun Valley. Gardeners may also wish to look into activities of the local chapters of the California Native Plant Society, including ones for Los Angeles and Santa Monica, San Gabriel Mountains, the Mojave, Orange County, South Coast and San Diego.

Some rules of thumb will apply wherever you are. If your hard-leafed plant begins looking burned, brittle and stressed, or if your soft-leafed plant wilts or the leaves feel hot to touch, water slowly and deeply. That water should be applied gently and evenly, and only when it’s cool. The mixture of hot, dry soil and water foments root rotting fungi and molds.

Finally, if Jett has said this once, she’s said it 100 times: mulch. Keeping the soil cool is essential to making the best use of water -- and preventing that water from killing the plant it’s intended to benefit.

Green's column on low-water gardening appears weekly on this blog. To read past installments, click on "Dry Garden" in the category cloud.