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Drought-Tolerant Plants: An Experiment

Are you interested in plants that will look good year-round without supplemental water in the summer? Just think of all the money and time you could save. It would also make it possible to add interest to areas such as under oak trees, by the mailbox or on slopes.

Several Master Gardeners and I are developing a preliminary list of plants that we are growing and monitoring for water needs and performance. We would like you to join us. Make your comments on the Master Gardener – Tuolumne County Facebook page.

There are many sources of information about drought-tolerant plants such as the U.C. Davis Arboretum list of “All Stars.” Their web site http://arboretum.ucdavis.edu/arboretum_all_stars.aspx has a drought tolerant search category.

Another good resource is “Care & Maintenance of Southern California Native Plant Gardens,” from Rancho Santa Ana Botanic Garden, available from the California Native Plant Society. This guide, published by the Metropolitan Water District of Southern California, identifies plants with very low water use.

Ultimately we would like to share information on three different levels of supplemental water needs. Having foothill-specific information will make it easier to assess what to plant, where to plant and what kind of water provisions to make.

1. No water, except when planted. This category includes both those plants that maintain an evergreen presence year-round and those that disappear in the summer, but not those that go dormant and look dead. Most must be planted in the fall and receive enough winter rain to become established by their first spring. Examples are California fremontia, matilija poppy, California fescue, bearded iris, Pacific Coast iris and California wild rose. Many bulbs are in this group, such as daffodils, Ithuriel’s Spear (Tritelia laxa, a member of the Brodiaea family) and several salvias, such as brandegei, white, and clevelandii. Many spring wildflowers, such as California poppies, Chinese houses (Collinsia heterophylla) and bush lupine are also in this group.

2. Water only until established. These plants benefit by being planted in the fall and then watered in the summer until established (1-3 years depending upon growth/vigor). After that they should not need water unless the summer weather is extremely hot and the plant shows signs of stress. Then deep, infrequent watering may be needed. Plants being considered for this category include western redbud, several salvias-such as brandegei, white, clevelandii (Allen Chickering, Whirly Blue, PozoBlue)-and Rhus ovata (sugarbush) and trilobata (basketbush). Varieties of ceanothus (Concha), manzanita (Howard McMinn), rosemary, cistus (rockrose), artemisia and Russian sage (Perovskia atriplicifolia ‘Little Spirit’) belong in this group.

3. Infrequent, but deep watering indefinitely. Most of these plants, once established need infrequent but deep (once a month) water during the summer as determined by signs of plant stress. Some of those being investigated are ceanothus (Yankee Point), manzanita (Emerald Carpet) and salvias-Bees’ Bliss, leucophylla ‘Figueroa,’ sonomensis ‘Fremont Carpet’, ‘Dara’s Choice’). Other choices are deer grass, lavender, yarrow, penstemons, euphorbia (Mediterranean varieties), hellebores, santolina, goldenrod (Solidago California ‘Cascade Creek’), bush germander and lambs ears (Stachys).

So let’s try some of these plants and report on our experiences. Comment on Facebook. Let’s all work together to save scarce water resources by finding plants that thrive in our foothills climate.

Marlys Bell is developing a demonstration garden on her property to showcase plants need no supplemental water.