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Using Wood Ashes


Wood ashes from a wood burning stove or fireplace can be used on lawns and vegetable and flower beds if you follow a couple simple precautions. Do not apply too much and test your soil pH every 2 or three years to monitor its effect. Since wood ashes are alkaline, about half as strong as limestone, in time they can change the pH of soil. This can be for the better or for the worse depending on the starting pH of your soil. To monitor the change, test the pH of your soil using a simple pH kit available at garden centers or bring a sample of your soil to the Kemper Center for Home Gardening for a free pH test while you wait. Once you know the pH of your soil you will be better able to judge the effect of wood ashes.

Most vegetables and ornamentals prefer a pH of 6.0 to 6.8. Testing your soil every two years or so should be sufficient for the average fireplace user. Wood ashes can be applied throughout the general landscape, to include lawn areas, flower beds, the vegetable garden and around trees and shrubs. As a general rule of thumb, do not apply more than 2 pounds per 100 square feet every 2-3 years. The more ashes you apply the more important it is to have your soil tested regularly. And, if by chance your soil is on the acid side, applying wood ashes can save you the purchase price of a bag of lime.

Wood ashes are high in calcium, but only contain small amounts of other nutrients. They provide essentially no nitrogen, 1-2 percent phosphate, 4-10 percent potassium and some micronutrients. Consequently, their use as a fertilizer is very minimal. Do not rely upon ashes as your fertilizer source.

Missouri Botanical Garden, 2001-2011