I work for the Extension Service, and the following is from one of our bulletins:

Wood ash and the ashes remaining after any type of plant is burned is of value to gardens because of the potash it contains. It should be used dry. Potash leaches from ashes and rainsoaked ahes from an outdoor fire have litle nutrient vale. Coal ash contains little fertilizer, but may have value as a soil conditioner or to aid drainage in heavy oils.

Wood ashes are comparatively high in lime content. They also contain some pohosphorus, magnesium and a small amount or other elements - all of which are affected by leaching if the ahses are not protected from rain and melting snow. The composition of wood ashes varies considerable, depending upon whether they are derived from softwoods or harwoods. Unleached hardwood ashes contain up to 6 percent potash, 2 percent phosphous, and 30 percent lime.

Wood ashes may be beneficial to soil in moderation due to its soil conditioning and aerating properties. In soils that are already high in calcium, one inch of ashes applied to the soil surface is a safe application rate. Repeated application of wood ash could result in accumulation of salts or calcium to cause toxic effects, especially on heavy textured, poorly drained clay soils.

Lignite coal ashes are high in lime and may contain substantial sodium. Sodium applied to soil increases puddling and crusting, water tends to run off rather than penetrate.

Hope this helps.

Marie B

I have read on a forum on this site (don't remember which one as it was about 6 months ago) that someone had used them around their peach trees and they had bountiful harvests after adding the wood ashes.

Just this year, I started adding wood ashes around our fruit trees. As a mulch around the fruit trees and in my garden, I use pine needles that I rake up from under my 4 pine trees.

Anything that needs potassium in the soil would benefit from the wood ashes.

After cleaning out the fire place Mama always made us put them around her roses.

I tilled mine into the soil for a few years now and the only thing that I have found that hasn't done well is a dwarf canna. It may not be due to the ash or it may. My banana tree doesn't seem bothered. Roses are very happy. Portulaca does very well. Iris are still blooming in October. Elephant ears are huge. Glads and daylilies do well.

I do have sandy soil. Great drainage. Maybe to Great. I have also started mixing in lots of compost. Can't wait to see the difference or lack of next year!

Lana

Thanks marieb for your info on wood ashes. I've got 10 gallons of ashes that I'm fixing to put to use!

Tom

They are also a barrier to snails and slugs. If a border is spread around an area, these pests are kept out. It does need to be replenished pretty often though.
Lina