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Fireplace or wood stove ashes can benefit garden


Robert E. Thomas
Information Specialist
University of Missouri Cooperative Media Group
Phone: 573-882-2480

Published: Thursday, Feb. 4, 2010

Story source:

David H. Trinklein, 573-882-9631

COLUMBIA, Mo. –Gardeners can use ashes from fireplaces or wood stoves to enrich their soils, said a University of Missouri Extension horticulturist.

“Understanding the effect of ashes on the soil is helpful in deciding how much can be added,” said David Trinklein.

Calcium in wood ashes raises soil pH. The amount of calcium varies with the species of wood. Hardwoods such as oak and hickory have more calcium than softwoods such as pine or spruce, he said.

On average, wood ashes have only about half the acid-neutralizing ability of lime. This means that if soil tests indicate the need for five pounds of lime per 100 square feet, it will take 10 pounds of wood ashes to accomplish the same pH change.

Test your soil before applying wood ashes. Most flowers and vegetables grow best in soils having a pH between 6.2 and 6.8. Test soil every year if you are adding substantial amounts of wood ashes. In the case of light applications, a soil test every two to three years should suffice.

Wood ashes will not work as a soil conditioner. The carbon compounds that act as soil conditioners in sawdust, compost and other wood products are almost totally consumed during burning.

Soil testing is available through local MU Extension centers or from the MU Soil and Plant Testing Laboratory. For more information, contact the lab at 573-882-0623 or, or visit the lab’s Web site at