A month or so ago a local guy I know who has a garden in a section of a town plot asked if I had any ash from my woodstove. He said it's good for the soil. I gave him several bags that I had saved.
I got a call from him today asking what the heck I burn in the stove. Hardwood, I told him. Well, it caused burns on his arms and hands. Hey, I'm not a gardener - I killed a cactus once - but a five minute online search told me that wood ash when mixed with water can become toxic.
Live and learn, I guess.