Thankfully, the fires surrounding Los Angeles are subsiding. CAL Fire reports most fires in the region are contained (except for the Thomas fire in Ventura County, which has burned more than 200,000 acres and is only 20% contained). But the air quality is still very poor and local trees and plants are covered in dust.
Thankful that our trees and plants are scrubbing the air for us, we were wondering if we should be washing the soot off the leaves. We checked in with our local expert, Carol Bornstein, director of the Nature Garden at the Natural History Museum of Los Angeles County, to see if we should be pro active or wait until the rains come, hopefully in the next few weeks.
“I have never seen direct damage to foliage due to ash accumulation,” began Bornstein, “I would not be surprised, though, if tender young and/or thin tissue is affected to some degree. Many of our native species have a thick, sometimes waxy cuticle on their leaves and that likely provides a physical barrier to the ash.”
Ash can also make soils more alkaline, explained Bornstein. While not a problem for most plants this is something to be aware of if one has acid-loving plants in the garden. She also noted there are various non-plant compounds in ash – from materials that burned in buildings, cars, etc. — which may contain toxins that could harm plants and animals…but it’s hard to know what’s in the ash without further analysis.
As a result, Bornstein suggested that hosing off all foliage and providing a deep irrigation garden-wide would be beneficial for plants and trees. Removing the layer of ash may also prevent a potential build-up of heat in the leaf, comparable to dust accumulation, another complication challenging for drought-stressed plants, explained Bornstein.
“This is the time of year that native plants and other mediterranean-climate species are expecting moisture, and we need to provide it now rather than wait until summer,” explained Bornstein.
Allaying our concern about wasting water, Bornstein suggested that “On the contrary, better to make up for this deficit now when it can do the most good.”