Could there be a more timely title for the gardener in the West? With increasing challenges to an equitable distribution of the West’s limited water resources, it behooves us all to give some serious thought to how we design and plant our gardens to use less water.
Olivier Filippi has given this subject serious thought for at least the last two decades, from the home base of his nursery in the southern France. He and wife Carla have traveled throughout the Mediterranean and other regions of the world with a similar climate, to study the native plants and their responses to the annual pattern of rainless summers. They have put that field research to work in their own garden, experimenting with hundreds of plants to see how they would survive with little or no summer irrigation in the artificial situation of a garden.
The long-awaited result is The Dry Gardening Handbook, now available in English following its first publication in French. Filippi begins with a whirlwind tour of the planet’s major mediterranean-climate regions, followed by a thorough discussion of the adaptations that allow plants to survive in those regions that lack rainfall during the warmest months.
Maps showing the Mediterranean-climate regions surrounding the Mediterranean Sea, combined with climatic diagrams for a number of major cities in the area, confirm the author’s primary focus on gardening in Southern Europe. But the information provided, particularly in the climatic diagrams, provides a model for analyzing the annual rainfall deficit in the western United States. Internet references are offered to help readers create their own diagrams—a most useful service.
Against this background of climatic constraints and natural plant responses, Filippi provides a complete recipe for choosing plants for an unwatered (or minimally watered) garden, and for planting and maintaining it. This information is solid, based upon the experiences in his own test garden. Having visited his magnificent garden in France, I can confirm that the author knows of what he speaks. He emphasizes the need to understand the characteristics of the soil and of the critical requirement for good drainage; to select plants that will hug the ground and shade it, thereby reducing moisture lost to evaporation; to avoid nursery plants with malformed root systems, thus unable to plumb the depths of the soil for moisture; to plant well and at the right season (autumn!); to water properly during the first year, so as to avoid watering in ensuing years; to weed and mulch to give each plant the greatest chance of success; and to acknowledge the value of pruning for many of the plants adapted to a mediterranean climate.
More than half of the book is devoted to An A to Z of Plants for the Dry Garden, an encyclopedia of over 500 plants that Filippi has tested in his garden; virtually all of listings are accompanied by generous text and his own beautiful photographs. He provides concise information on the origin of each plant, its size, exposure preference, hardiness (expressed in degrees Celsius, rather than in zones), and drought resistance code. This last item is an invention of his to categorize plants according to the amount of drought each can tolerate and still thrive. Plants are rated from 1 to 6, where the lower figure suggests a tolerance for about one month without water, and the higher figure as much as six months without. This may be the first attempt to quantify a plant’s tolerance for drought, and is one of the most valuable features of the book.
Filippi emphasizes that soil conditions and microclimates will influence a plant’s drought resistance capability. I compared the experiences in my own unwatered garden with those in Filippi’s book. Plants such as rosemary, lavenders, and bottlebrushes survive without irrigation for six months each year, thus rating a 6; the same plants typically received a rating of only 4 in Filippi’s garden—undoubtedly proving that my clay soils and milder San Francisco climate allow plants to survive for longer periods without rain or irrigation than those in the sandier soils and greater exposure of his garden. The model can be applied to other plants, wherever we grow them. The result might just be a substantial decrease in the amount of water applied to our gardens, without losing their beauty and diversity. As Filippi points out, the floras of the world’s mediterranean-climate regions are among the most diverse; there is no risk of running out of beautiful plants with which to fill our gardens.
In the July ’08 issue of Pacific Horticulture, we began the first in an occasional series on rain-only gardens. The Dry Gardening Handbook should be a bible for those who wish to follow that lead and create their own minimally irrigated gardens.
Richard G Turner Jr, editor