Yes, used sparingly, wood ashes contain 3 to 7 percent potassium plus an array of other nutrients in lesser amounts. Wood ashes, however, also decrease soil acidity. I would think the best thing to do is to mix them into a compost mix you are using.
If they have been out in the weather for too long they lose their potency, and you need to be careful that they are 'clean' and not the result of other things like coal or worse plastics, being burnt.
I used to add a handful to my mix in the square foot garden where I added three or four handfuls of compost, one of ashes, and one of blood, fish and bone, to each square foot before mixing it in.

much appreciated thanks jim