Next time use it as topdress at the end of the season.
it's free and full of nutrients
Be very careful, cautious, and mindful when you do this. This is very true, and good practice both, but if you burn something like laurel or rhododendron wood, and theres some others too, and you put a little too much down over a clay rich soil, itll harden the top layer of soil almost like cement, and itll drive the top inch or two of topsoil to like 9 ph after a couple of rains.
The lye that leaches out from many woods, is like 13.5 on the PH scale,
its up there with caustic soda as far as it's alkalinity goes.
Tree
Hardwood ash only
if you use wood, no burned colored cardboards is a good thing to stick to as well. and def only put a dusting down, and not frequently either. The soil alkalinity it causes over time will eventually kill the soil fungi, and lot's of terrible,
very unwanted things will happen after that in an "everything all at once" kind of way, even if it's seemed fine for a while before it.
Using ash inappropriately the lye can actually completely, and permanently ruin a given soil mass for growing plants of any kind at all. And the only way to fix it would be to backhoe the soil out, and refill it with healthy soil.
When a forest fire does this naturally, its (supposed to be) rare, and in a given square footage of soil, there is actually very little ash deposited, and it's mostly from
leaves, whos ash contains far less Lye then wood ashes.
I actually spread laurel ashes into the gravel in my stepping stone walkways because it alkalizes the soil so effectively, no weed will grow from it, not even dandelions and bull thistle. It hardens the gravel in place nicely too, and rinses right off the rocks after pouring.
in what world do you only get that little bit from 12 plants ??? It was a glorious few years tho cuz you could sell “ overages “ to the few dispensaries that were around and they were payin WELL
outstanding 
