Clients often mention"drought-tolerant" as a quality they want in their plants as we plan a new garden. Here in the Bay Area, this would include California native plants as well as plants native to South Africa, New Zealand and Mediterranean regions, which are climates most similar to ours.
This past August, I traveled to the south of France where the typically lush gardens of summer were replaced by bare, scorched earth and dried trees. Because of severe drought and punishing triple digit heat, residents collectively took the extreme measure of turning off all irrigation watering to conserve water. What resulted had me wondering if drought-tolerant is even possible.
The beautiful gardens of Provence were reduced to compacted, dusty soil and trees with few leaves. Even the lavender, a staple fixture there and considered to be drought-tolerant, was nearly dead throughout the region.
What do we mean when we say drought-tolerant? We want it to be true that there is a group of plants that thrive in a warming climate and don't need any watering at all. But as I saw in France, without regular watering, almost every plant won't make it under intense heat. Plants in the shade have the best chance of surviving, so the need to plant trees and create shade is urgent now as temperatures soar.
I found this wildflower growing in very dry soil in the hot sun and was a good example of a drought tolerant plant. In addition, conifer trees were still green without watering, however most everything else was desperately dry and unable to stay green or keep leaves on its stems. They needed some form of regular watering to survive.
When we say "drought-tolerant," what we want are plants and trees that:
* Can withstand intense heat
* Don't need a lot of watering, but needs consistent and efficient watering. This can best be achieved from a low-flow drip irrigation system with emitting line around the roots (remember, tree roots are not at the woody trunk but further out in a diameter).
* Can tolerate compacted soil from intense heat, but also responds well from turning the soil around its roots and a layer of mulch to preserve soil moisture.
What we don't mean by drought-tolerant are plants that thrive without any watering at all and no attention to soil health. Leaf blowing in the planting beds for example, is terrible for soil health because it takes away valuable top soil and compacts stressed soil even further, exposing tree roots and drip lines. No leaf blowing in the planting beds, please.
There was one exception I saw in France that was thriving on nothing in intense heat and produced delicious, abundant fruit.....
The fig tree! They were thriving with no watering in triple digit heat. Figs also do very well here in the East Bay. I've joked instead of Oakland, we could have been called Figland (or Plumland : ) So let's plant more fig trees (though there's the problem of the squirrels eating the fruit, but that's another discussion...)
Drought-tolerant is a complicated idea but important to consider and discuss. I hope this fall brings rain and cooling temperatures. I'll be planting more trees and encouraging shade where I can to accommodate the heat that's inevitably here to stay.
