I was in shock and awe when I saw it for the first time. When I asked why she would do such a thing, she told me she would prefer to conserve water than to irrigate a lawn that no one used. Perhaps she was not as crazy as we all had thought. Although most of us loathe red lava or other rock, some loathe yard work even more.

"Hardscape" generally refers to useful paved or decked surfaces such as patios, driveways, walkways, decks or porches, but the term also includes areas covered with gravel, rock or coarse bark (if the bark is a relatively permanent feature, not merely used to cover soil until landscape material becomes established). Hardscape certainly epitomizes drought-tolerant landscaping. Although gravel and rock seem to be very practical, I do not know of a single landscape designer who would recommend it.

Fortunately, many drought-tolerant species of plants, including many native ones, are available for drought-tolerant landscaping. Although they can survive with considerably less irrigation or none at all, and generally require less maintenance than other plants, most of them are not necessarily more resilient when faced with other adversities than are more traditional species. For example, few of the woody shrubby species recover well from severe pruning.

The most common adversity drought-tolerant species encounter is, ironically, excessive irrigation. Mixing drought-tolerant species with those that require regular irrigation is almost never successful. Even if soil is not often saturated, regularly applied moisture that is necessary to sustain the more traditional species or lawn promotes root decay of species that prefer dry conditions. Fungal organisms associated with decay are, incidentally, more active during warm weather, but many plants are more susceptible during winter while not as vascularly active (as they were while dormant).

Every species prefers specific volumes and frequencies of irrigation and will thrive within a reasonable range of these preferences. Some are certainly less critical than others. For example, rhododendrons will not survive long without regularly applied irrigation. However, lily-of-the-Nile can survive with minimal irrigation or tolerate excessive irrigation, depending on the flood level of the Nile River. Of course, weather conditions such as temperature, humidity and wind affect how much moisture is dispersed by evapotranspiration (evaporation from foliar surfaces) and therefore affects how much irrigation will be needed.


Flower of the Week: Candle delphinium

Brent Green, my former college roommate who is discredited regularly within the context of this column, first introduced me to candle delphinium, Delphinium elatum, in the front garden of one of the residences in San Luis Obispo that he maintained. It instilled shock and awe, like a lawn of red lava rock. The flowers were as tall as eight feet and were as blue as the uniforms of the Prospect Panther cheerleaders.

"Pacific strains" are the most popular of the candle delphinium, but are actually hybrids with another species. Shorter varieties are as compact as two feet, but the more popular are about six feet tall. Most bloom with various shades of blue, but some bloom white, purple, lavender or even pink.

Those that bloom early may be cut back to encourage secondary bloom during autumn. Full sun exposure, rich soil, regular irrigation and regular application of fertilizer are preferred. Snails may become a problem. Tall floral stems should be staked.

Horticulturist Tony Tomeo can be contacted at 408-358-2574 or at LGHORTICULTURE@aol.com.