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Using Wood Ash Wisely


Question. Hi Mike: Is there a way to use fireplace ash that would be beneficial to my garden or lawn? If not, what is the best way to dispose of the stuff?
            ---Chris in Berwyn, PA (formerly Newport, RI)

Mike: Like many of my neighbors here in Eastern Carolina, I have a 'burn pile' where I dispose of storm debris, old trimmed branches (mainly pine and oak) and all manner of other garden/yard items. My question is: Is the leftover ash good for anything? I know better than to put it in the compost pile. Thanks,
            ---Doug in Beaufort, NC

Answer. Thank you, Doug. As you note, I've long cautioned gardeners not to include anything other than very small quantities of wood ash in a compost pile—a little of this highly alkaline material goes a long way. But those of us with naturally acidic soils can (and should) use much larger amounts on our lawns and gardens—as a substitute for lime.

Before we get to that, however, I'd like to take a moment to try and pry your incendiary little fingers away from those piles. Yes, we guys love to set stuff on fire—especially in the name of 'yard work'. But such burning fouls the air, adds greenhouse gases we don't need, and wastes lots of nutrients. Pile up your "garden/yard" items and they'll turn into nice compost, especially with lots of leaves in the mix. Stack the branches on the outskirts of your property to provide habitat for toads, birds and other beneficials. (And you'll find a surprising amount of compost at the bottom of those piles after a few years.) If you can't go completely 'burn turkey', consider cutting back to one small bonfire a year to satisfy your inner firebug, and get better use out of the rest of that wood.

And good quality hardwood ashes—that means no ashes from BBQ grills, cardboard, plywood, painted, or pressure treated wood—do have real agricultural use. (Softwoods have a lot less value, but you shouldn't be burning soft wood in a stove or fireplace anyway.) The best information on how to properly utilize the valuable material in wood ash is contained in a couple of great farm-scale articles from the Georgia Extension Service and the government of Alberta's department of Agriculture, Food and Rural Development. We'll post links to those articles at this end of this Q of the Week for those of you who want all the details.

To help put the advice into garden-size perspective, we turned to Julia Gaskin, a Land Application Specialist for the University of Georgia Extension Service who recently updated their wood ash information article. She explains that ash from good quality hardwoods contains a very nice amount of potassium; at least 3% by weight. Also known as potash, this is the "K" in the fabled N-P-K scale of plant nutrients—the Dow Jones of Horticulture! Potash improves root health and strengthens the very cellular structure of plants, helping them resist all kinds of stresses.

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You Bet Your Garden   Question of the Week  ©2006 Mike McGrath