Peonies like alkaline soil and the potassium may also be helpful. Just try a little if you haven't used ashes before, and maybe get a soil test if you don't know much about your soil. Adding ashes to soil that is already alkaline, or adding too many ashes, could be damaging. The "dangerous" chemicals in the ashes are quite soluble, so you can add a little and then add more in a month or two when they have washed away. If your soil is acid or deficient in potassium then you might get quite spectacular results from using the ashes. Also think about trying a phosphorus fertiliser like bonemeal if you haven't before.

I have never used fertilizer on my peonies but have regularly added compost to the soil around the bushes. When I had my soil tested I had 4 times the minimum potassium and phosporus. I was short a little on nitrogen and vegetative matter which the compost takes care of. A soil test is worth the expense. Al

The following is an opinion only:

Alrics, have you ever heard of lye soap? In the old-fashioned way of making lye soap, ashes from the stoves and fireplaces were placed in a wooden box and water poured over them. The liquid that came from it has a very high pH. This is 'lye' or 'caustic'. (It's then cooked with animal fat to make soap, but that's another thread.) The rainwater hitting the ashes in the outdoor fireplace will have leached some or even most of this lye. If the water could drain away, then it may have taken the lye with it, but it will also have lost the good stuff, such as potassium, also.

Bottom line, I wouldn't use the ashes from the outdoor fireplace.

As for the indoor ashes, I dust my peony beds with ashes regularly, but lightly, being careful to keep the ashes from actually touching the plants. I add sheep manure, which tends to lower the pH, regularly also. The peonies seem to like the regimen. (I have to admit, I do it this way because it's the way my mother does it. I started working on the explanations later.)

Ray

Yeah, do be careful with ashes. My mother-in-law told my husband that his grandmother use to dump the ashed from the wood-stove on her peonies and she had the best peonies around. Thus, he started dumping ashes on my peonies, ashes from the bbq, ashes from stuff he burnt, etc., he didn't differentiate between what type of ash. You know, if a little is good, a lot must be wonderful.. He almost killed off a nice healthy row of peony. He's not allowed near my peonies anymore....

Diann
IA Z5a

if a little is good, a lot must be wonderful Men!!! Your MIL had the right idea, little and often. And its probably best to stick to wood ash.