Wood ashes safe to use on garden

Q. Can I use wood ashes from the fireplace on my vegetable garden?

Jason from Liberty

A. Yes. Wood ashes can be a great soil amendment for the vegetable garden. That is, of course, assuming firewood is all that is entering the fireplace, wood- burning stove, or outdoor furnace. Anyone burning trash or other items should not be using their ashes on gardens where food is produced or plants are grown.

According to our experts, wood ashes contain nearly all the essential nutrients needed for plant growth. Wood ashes contain about 1 percent phosphorous, 3 percent to 5 percent potassium and small amounts of micronutrients.

More importantly, the wood ashes affect the pH. The calcium in wood ashes makes it similar to agricultural lime. Thus, the ashes will raise the soil’s pH level.

Our experts at Iowa State University say that wood ashes have a high-water solubility, and thus will react more quickly to change the soil pH. This is helpful if you have acidic soil and need to raise it to the recommended 6.2 to 6.5 pH needed for most vegetable plants.

If you are using your soil test recommendations and need to convert lime calculations to the amount of wood ashes needed, it’s usually quite simple. In general, 2 pounds of ashes are about the same as a pound of lime. This can vary, though, depending on the type of wood and other factors.

It is also recommended not to put more than 2 pounds per 10x10 garden space. Always be sure to take a soil test to be sure you are not adding too much of a good thing. Soils with a high pH will not be improved by adding wood ashes.

Use caution when working around the ashes. You should wear a dust mask and other personal protective equipment. Treat ashes the same as powdered agricultural lime when applying it to the garden area.

Finally, do not use nitrogen fertilizers for at least a month after wood ash application. The fertilizer can react with the ash, wasting money and time.

For more details, visit go.osu.edu/woodash.

Eric Barrett is OSU Ext. educator for agriculture and natural resources in Mahoning County. Call the office hotline at 330-533-5538 from 9 a.m. to noon Mondays and Thursdays to submit your questions.