Planning a drought-tolerant garden can be a challenging endeavor. Knowing which plants to use and where to plant them is difficult, as information and advice can vary significantly. However, there are a few simple things you can do to make the process easier.
The first task is to become intimately acquainted with your garden. Watch the way the sun moves and where the shade falls throughout the day. It may seem obvious that how much sun a plant receives will affect how much water it uses, but not all plants labeled for low water use will thrive in full sun.
Knowing the locations in your garden that receive shade from summer heat can greatly affect the health of your plants and the maintenance required to keep them looking attractive.
Note how wind moves through your garden. Evapotranspiration, the loss of water through plant leaves, increases significantly with high, hot or dry winds. On a cloudy, yet windy, day the plants in your garden could dehydrate more than you expect.
Finally, get up close and personal with your soil. Check its water retention by digging a hole about a foot deep and wide and filling it with water. Hope for the water to percolate through in about an hour, signifying good drainage.
Many drought-tolerant plants, especially succulents and cacti, will rot if soil drains too slowly. Conversely, if the soil drains too readily, it can be difficult to keep even low-water plants adequately hydrated.
All of these factors will help you form a picture of how water will be utilized in, and move through, your garden. This knowledge is a useful tool when choosing new plants.
When working on creating a drought-tolerant garden there are some preconceptions it is best to discard. When many people think of a garden, the image that comes to mind is of a classic English garden. This is understandable as modern home gardening and many of its traditions originated in Europe.
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But England has a different climate than Napa, and it is not realistic to expect our gardens to look like English landscapes.The plants found in English gardens are often not good candidates for a Napa Valley garden, least of all a drought-tolerant one.
Many of the best-known annual plants are thirsty in our climate, as are many popular perennials such as hydrangeas, camellias and gardenias. Tropical plants, while visually stunning, are often troublesome as well. Even if they are not labeled as requiring a lot of water, the relatively low humidity in Napa Valley can make it difficult to keep them healthy.
Changing our expectations for our gardens does not mean lowering them. A garden can use less water and remain visually pleasing, lush and colorful. In a sunny location, shrubs such as salvia and lavender can be placed among large succulents such as aloe and agave. The contrast of soft and sharp textures is pleasing to the eye. The salvia will bloom most of the summer, while many aloe, such as Aloe capitate, bloom in the winter.
Many popular groundcover-type plants have shallow roots and need frequent watering. These can be easily replaced by a clumping or vining succulent. A favorite of mine is ice plant, Delosperma cooperi, which produces a carpet of purple-pink blooms from spring through summer.
Identifying plants that work in a drought-tolerant garden is easy after some practice. Generally speaking, plants with large, glossy leaves are a poor choice. These plants will lose a lot of water to evapotranspiration and are prone to sunburn. Plants with dusty or fuzzy-looking leaves are much more adapted to hot, dry conditions.
The roots of a plant can also tell you something about its water needs. Small, shallow roots will need more frequent watering than large, deep-burrowing ones. Never hesitate to gently remove a nursery plant from its pot and inspect the roots. They are a key indicator of plant health.
An important bit of information often missing on plant labels is the term “once established in the ground.” Succulents excepted, a potted plant will usually need more water and fertilizer than the same plant in the ground. Many drought-tolerant shrubs survive by growing broad or deep root systems. It takes at least a year for new plants to develop a useful root system, during which time they will need additional water.
Knowing these facts about your garden and the plants in them, as well as altering your perception of how a garden should look, can make an enormous difference in your relationship with it. You can minimize required maintenance and reduce your stress, leaving only the pleasure of enjoying the beautiful space you have created.
Next workshop: “Home Vineyard: Part 2” on Saturday, Sept. 14, from 9:30 a.m. to 2 p.m., in Calistoga. Learn techniques to maintain your new or existing home vineyard. Workshop location will be provided after registration. For more details and online Registration go to http://napamg.ucanr.edu or call 707-253-4221.
The UC Master Gardeners are volunteers who provide UC research-based information on home gardening and answer your questions. To find out more about upcoming programs or to ask a garden question, visit the Master Gardener website (napamg.ucanr.edu) or call (707) 253-4221 between 9 a.m. and noon on Mondays, Wednesdays or Fridays.