Ask Mr. Smarty Plants

If it's not No. 1, "What's wrong with my weeping willow?" is right up there close to the top of most frequently asked questions to Mr. Smarty Plants. If you search on "weeping willow" in the Ask Mr. Smarty Plants section, you get thirteen possibilities. The problem is, the question is the wrong question asked at the wrong time. We wish that gardeners would ask "Should I plant a weeping willow?" BEFORE they purchase and plant it. Non-native to the United States, Salix x sepulcralis is a hybrid of a Chinese species (Peking willow) and a European species (white willow), and is said to grow in Zones 5 to 8 in the United States. It is weak-wooded, fast-growing and, therefore, short-lived. It has aggressive roots, can lift sidewalks and interfere with sewer lines, often growing on soil surface, making a problem with mowing. It is susceptible to a number of pests and diseases, and notorious for littering the ground beneath it. See this University of Florida Extension website on Weeping Willows for more information. Also, in case you think we're exaggerating, see this Q&A from North Dakota State University Extension on weeping willows.

We tend to agree with you that terrible fires in California recently could very well be causing the problems on your tree. The Salix x sepulcralis is considered a poor urban street tree, precisely because of pollution issues. Your location in north central California would certainly add credence to your idea. Not only would your trees and those of your neighbors have been dealing with wood smoke, but also with all the other possible pollutants from man-made structures that burned. Sadly, there is probably not much that can be done. You might try the thumbnail test, scraping away a thin bit of bark from some of the tree branches. If there is green underneath, the tree is still alive. If you want to retain the tree, we certainly wouldn't recommend doing any pruning on it until cooler weather, when it should be more dormant. In the meantime, giving it some extra water and watching for any possible diseases attacking the weakened tree might help it pull through. Then, you could try pruning away any branches that are obviously dead, and taking off some tops to take some of the strain off the roots in getting water and nutrients up to the top.

Because this is apparently a widespread problem, we would suggest you contact your University of California Shasta County Extension office. They should be aware this is going on, and if there are any cures, should be able to advise you.