Are drought-resistant gardens going to drown in the deluge? That’s the question being asked by people who have recently planted one.
Actually, most drought-resistant plants are used to the rain and are probably enjoying it. “They’re accustomed to deluge and dearth,” said horticulturist Randall Ismay of Water and Landscape Management, “because most are from climates like our own where winter is typically wet but summer dry,” what are called Mediterranean climates. It doesn’t matter if the winters are wet, even really wet, as long as the summers are dry, or nearly so.
However, if there are going to be any casualties among your drought-tolerant plants, they won’t be apparent until spring when a higher sun and warmer temperatures stress plants affected by water molds. Water molds attack the roots of plants when the soil is wet and airless and they can kill a plant.
Also called root rots, water mold fungi, especially some named Phytopthora are the leading cause of death in plants and there are “a plethora of phytopthora” in California soils, according to Ismay.
They thrive when water keeps air from moving through the soil, which happens when plants are watered too often, when soils are too dense and “heavy” or when it rains too much.These diseases are the reason for recommendations of “good drainage” and “not watering too often.”
The diseases are active at all times of the year, but typically their damage isn’t noticed until the weather warms, when they are most active. Affected plants seem to wilt, though this is not caused by too little water, but too much.
We have had so much rain that it will take weeks for the soil to dry enough to discourage water molds and the only thing to do now is to be sure and not water, “for at least five weeks,” Ismay said.
Don’t be fooled by the temporary drying caused by Santa Ana winds. The soil next to the roots is most likely wet despite the dry appearance of the surface.
Since more rain is sure to come in February and March, there is probably no need to water drought-resistant gardens until sometime in April or even May.
A few plants are especially sensitive, including some rock roses, the native Fremontodendron , ceanothus, tulip trees, a few pines and an acacia or two. Generally, older, mature plants are the ones most susceptible.
If a plant shows signs of stress this spring, and it is an important element in the garden, you might try a chemical sold under the name Subdue. It can suppress phytopthora, according to Donald Hodel, environmental horticulture adviser for the L.A. Cooperative Extension. It may be too late to save the plant once its distress has been noted, but it may be worth a try on valuable plants.
Where a plant has died, suspect a too heavy soil and poor drainage, which can be improved by adding organic amendments to the soil before you plant something there again. Better yet, plant something that is not so sensitive, and most are not. Most drought-tolerant plants are also tolerant of wet winters.
They are thoroughly enjoying all the rain. It’s been a long, dry drought, and that cool glass of water from heaven is much appreciated. It will help them through the long, dry summer ahead.