Photograph courtesy of Joy Hulme

Mexican evening primroses, like these which have taken over a portion of Joy Hulme's Monte Sereno backyard, are hardy, drought-tolerant plants with attractive blooms.




Less is more when watering most drought-tolerant plants

By Tony Tomeo

When I was in college, California native plant species and drought-tolerant species were very trendy. I never went along with trends and, at that time, continued to study North American maples.

I did not disagree with the usefulness of drought-tolerant species. However, it bothered me that so many people were interested in these plants because they were the trend. They tried to grow and cultivate them using the conventional methods used for introduced species that had dominated the industry.

I think almost everyone can appreciate the concept of using plants that require less water. Unfortunately, many landscapes designed for water conservation are often irrigated just as generously as other landscapes. Not only is water not conserved, but the plants may not be able to tolerate so much water.

I often see landscapes designed by those who want to adhere to the trend, so they use a few drought-tolerant species in landscapes that require copious irrigation. I have even seen annuals labeled as drought-tolerant "because they were grown with less water." This is a total scam. Limiting water does not change genetics.

If California native plant and drought-tolerant species are used to conserve water, they must be used properly. It is helpful to know how each species behaves and for which situations it is best suited.

Remember that you can take plants out of the wild, but you can't take the wild out of the plants. Every species responds in its own way to various stimuli. Every response has its justification. Likewise, growth habits are more functional than most people realize.

Coast live oaks in the wild extend their canopies to the ground and usually spread low and broad. The outer surface of the canopy will usually slope more shallowly on the side exposed to more wind. This structure is somewhat universal with the species, whether they are large individuals, or collective groves of smaller trees. The justification for this structure is aerodynamics. Rather than allowing wind to blow through the canopy, the coast live oak directs wind up and over itself. Although this is not often seen in home gardens or densely forested areas, trees will try to structure themselves appropriately if given the chance.

Another example is the Monterey pine, which plans ahead for the forest fires that occurred regularly here prior to modern development. Mature trees retain many of their dead branches and needles to make themselves as combustible as possible. If they burn quickly and completely, the seeds distributed in the heat are not killed and will not have competition as they start to grow.

There is much more trivia than I can write about. My point is that if you know how a species behaves in the wild, you will have a good idea of what to expect from it in the garden.

Many drought-tolerant species are showiest in the winter or spring because they expect summer to be too warm and dry for any activity. Another common distinguishing characteristic is small leaves, which lose less moisture than large leaves.

The few drought-tolerant plants that are not harmed by too much irrigation may instead respond by excessive vegetative (nonblooming) growth. Native Joshua trees, for example, are often landscaped around rather than removed. If given too much water, they can grow so vigorously that they cannot support their own weight.

A good place to see successful drought-tolerant landscaping is in Guadalupe Gardens, lining Taylor Street at Spring Street. Many practical plants are included in this garden and allowed to exhibit their natural characteristics.

An excellent nursery to purchase California native plants is Yerba Buena Nursery at 19500 Skyline Boulevard in Woodside, at 650.851.1668. There also are many drought-tolerant species not native to California. Outside of reputable nurseries, they may be more difficult to recognize.

Sunset's Western Garden Book has a list of excellent choices and describes them thoroughly. Just remember that the book is written for a very large area of the continent and it is not a catalogue.

Flower of the Week: Mexican Evening Primrose

One of the most reliable of the showy native perennials, Mexican evening primrose, Oenothera berlandieri, thrives with only minimal maintenance. It can actually be invasive if not contained. Full sun exposure is preferred, but any soil will suffice. It's an excellent choice for areas where nothing else will grow. Minimal irrigation is appreciated during the hot, dry part of summer, or while plants are getting established. (It is advisable to plant in winter so that roots are distributed somewhat by spring). Generous irrigation will not kill the plants, but bloom may be diminished.

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Horticulturist Tony Tomeo can be reached at 408.358.2574.

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