I've used black locust ash for many years in my garden which thrives!  In fact, I had a problem with my broccoli and brussels forming leaves but few heads, and after trying many different soil amendments found that wood ash (incinerated at high heat) solved the problem.  I have gorgeous heads now and the largely black locust wood ash was the only variable which changed. It's a great wood for flooring, siding and beams, just saying.  It's had a bad rap.