The recent fires in Southern California have been distressing to all of us who live here and those who have family and friends that have been affected. I am one of the fortunate ones who hasn't been directly affected. The worst that I have had to deal with is bad air conditions and a little falling ash.
Actually the worst of the ash falling was a couple months ago during the Zaca Lake Fire. For days we watched the fine particles of ash falling on Santa Barbara and coating the sidewalks, our cars and our gardens. I wondered then what kind of effect the ash would have on plants. Would it be somehow beneficial to my garden? It would be nice if it was some sort of fertilzer, wouldn't it?
After looking through a couple of my gardening books and giving it a quick Google, I found out that ash could be benefical to some plants.
Wood ash can be a good source of potassium, so that's good for soil that has a potassium deficiency. I've never tested my soil, so I have no idea if my soil has a potassium deficiency. Also, wood ash will tend to make your soil more alkaline. Good news if your soil is highly acidic and you want to balance it out more.
The bad news is that it won't be particularly good for any acid loving plants. These include Azaleas, Cyclamen, Impatiens and Primula to name a few (a few that I happen to have in my garden).
Since you can't get rid of the ash in your garden, apparently the only thing to do is to water it in as best you can. I will also be sure to give some acid fertilizer to my acid loving plants, and hope for the best.