Drought tolerant ornamental oregano.
Plants are made up of 85 to 90 percent water, but they use less than 5 percent of the water that passes through them in plant processes. The rest is lost to evaporative cooling and transpiration. We have to irrigate our landscape and garden plants efficiently and make every drop count so plants receive the optimal amount of water for health, without wasting a precious resource.
We are in another drought. The Truckee Meadows Water Authority is asking that homes and businesses in Reno/Sparks reduce their outdoor water use by 10 percent, because Lake Tahoe and the other reservoirs are extremely low. While this doesn’t sound like much of a reduction, plants that aren’t drought tolerant may suffer.
Some plants have physiological mechanisms that help them avoid drought stress. Drought resistance or resilience is actually the avoidance, postponement or tolerance of dehydration. A drought-resilient plant can usually resist injury and survive water stress.
Some plants escape drought. They go dormant during the drought and regrow when water is once again available. Kentucky bluegrass turns brown under limited water availability, yet can often come back when water is restored, unless the water deficit lasted long enough to kill it. Others, such as desert wildflowers, complete their life cycle during favorable moisture conditions. Some plants tolerate drought by reducing the water lost by closing down the pores on their leaves and developing a thickened cuticle. Or, they may lose leaves or grow less, so they need less water. Some can change the angle of their leaves or curl them, so there is less leaf surface exposed to the drying sun. Others have hairy leaf surfaces or spines that shade the leaf and reduce water loss. Another adaptation is coloration. Gray leaves absorb less sun, stay cooler and therefore lose less water. Notice that many of Nevada’s native plants, such as sagebrush, are gray-green in color.
Roots have a big impact on drought tolerance or resistance. Deep roots, such as tall fescue has, can keep drawing up water until the drought reaches deep into the soil. Under water stress, some plants grow more spreading roots and root hairs to better mine the soil for water.
In our arid climate, when we design our landscapes, or need to replace or put in new plants, we should focus on using drought-resilient species. This will provide a more sustainable landscape during times of drought.
JoAnne Skelly is the Carson City/Storey County Extension educator for University of Nevada Cooperative Extension and may be reached at skellyj@unce.unr.edu or 887-2252.
