Laidback Gardening with Robert Kourik
Some golden rules of a drought-resistant landscape
A drought-resistant landscape can be as beautiful as any “real” landscape
Many of us have been brainwashed by glorious full-color books, mail-order catalogs, and magazines about herbaceous flower borders. Just about all of these are written and published in the rainy, humid areas of the U.S. or in England.
You can, however, design a drought-resistant garden with a riot of spring and early-summer color that rivals that of any other herbaceous flower border, but the types of plants are very different.
All droughts are not created equal and all native plants are not equal
In Occidental, for example, the rains average 58 inches. When the landscape gets wet, it really gets wet.
Eriogonum giganteum (St. Catherine’s lace) is native only to the Santa Catalina and San Clemente Islands off the coast of southern California. With a winter rain of less than 45 inches, St. Catherine’s lace is drought resistant, but unable to survive Occidental’s winter deluge. It’s a native California plant that really doesn’t belong in that part of Sonoma County. But with winter rains below 45 inches in the Kenwood area, St. Catherine’s lace thrives. But be sure to plant it, and other California native plants, on a gentle mound four to six inches high.
Many drought-resistant landscapes don’t need much supplemental irrigation
Oddly enough, many definitions of drought-resistant landscaping refer to reducing outdoor water use by “up to 75 percent.” Yet, by my working definition, the ultimate goal is to design, install, and maintain an ornamental landscape with plants so well adapted to their environment that very little supplemental irrigation is required.
One of my “test plots” was a small planting of various varieties of lavender, santolina, rosemary ( Rosmarinus spp.), a richly-colored “Bronze” fennel ( Foeniculum vulgare var. azoricum), a low, prostrate form of summer lilac ( Ceanothus hearstiorum) and a single, glorious specimen of Osmanthus “Silver Jubilee.” This small planting was watered only once a month the first summer after planting in the fall and received only two irrigations each year after that. This saves a lot of water. Please note, fall is the only time you can plant to have this independence from irrigation. The roots grow all winter and can easily adapt to the drying soil in the spring and summer. When planted in the spring, the roots can’t grow fast enough to keep up with the drying soil.
Drought-resistant plants must have good drainage
Most drought-resistant plants must have absolutely perfect soil drainage. These plants should be planted in a gravelly soil with very little clay loam or organic matter, and each plant must be planted on a raised mound to further encourage drainage. I avoid placing mulch near the base of the plant to prevent stem or trunk rot. Any summer watering should be applied some 18 to 24 inches away, outside the planting mound, from the base of the plant.
The best droughtresistant landscapes are planted by home gardeners
Drought-resistant landscaping is rightfully the dominion of the inspired, conscientious, and thoughtful home gardener, because only the homeowner can easily work within the pattern of nature’s seasons—planting only as the fall rains begin. Professionals have to plant all year to make a living.
Native plants are not always the most drought-resistant
There are a handful of Mediterranean climates throughout the world besides California—the Mediterranean basin, of course, the middle elevations of the Chilean mountains, portions of South Africa, the Canary Islands (with less than five inches of rain), and parts of Australia. Most of these climates are cousins to our Californian Mediterranean ecosystem and droughts are often more severe and the rainfall considerably sparser. Plants from these areas will retain their superior drought-hardiness.
An article in Pacific Horticulture magazine entitled “A Trial of Drought Tolerance” stated, “It is more sensible to choose plants for their adaptability to the site than for their area of origin. Except in the hands of an enthusiast for California native plants, a drought tolerant planting will probably be more beautiful and satisfying if well-chosen exotics are included.”
Robert Kourik is the author of 18 books on gardening, including “Lazy-Ass Gardening” and “Understanding Roots.” For a full list, visit www.robertkourik.com.