Ask The County Agent: ‘Can I use fireplace ashes in my garden?’

By Stephanie R. Butcher
County Coordinator Agricultural & Natural Resources Agent

QUESTION:  Can I use fireplace ashes  in my garden? 

Stephanie R. Butcher

Agent:  Yes, but only in moderation. Wood ash has calcium, magnesium and potassium (also called potash) that are great nutrients for your plants. Wood ash has a liming effect on your soil though, so it increases the pH like lime does. You should test your soil before applying any ashes. If your soil sample does not recommend lime, then you should not apply wood ash either.

The reason for testing your soil is to make sure that plants can absorb the nutrients they need to grow strong and healthy. A pH that is too high (basic) or too low (acidic) limits a plant’s ability to absorb important nutrients.

It is important to know what your specific plants need. Although the average vegetable and ornamental plant grows well in a slightly acidic soil with a pH between 6.5 and 6.8, some plants prefer a more acidic soil. For example, you do not need to add wood ash around acid loving plants like azaleas and blueberries. These plants absorb nutrients best in a soil with a low pH, so if you add wood ash to the soil around these plants, then it can hinder growth.

Continued use of wood ash in the garden can raise the soil pH too much and could even prevent plants from growing at all in the area. I worked with a client several years ago who brought in a soil sample from an area of his yard where he could not get anything to grow. The results came back with a pH of 8.1. It was the highest pH that I had ever seen on a soil report. After talking with the client, I found out that he had been putting ashes from his fireplace in that area for several years.

A good rule of thumb is to add no more than five pounds of wood ash per 1,000 square feet per year and soil test at least once every two years. It is also worth noting that wood ash should not be added to compost piles since compost needs an acidic environment.

For more information about soil amendments for your garden, contact the Coweta County Extension office at 770-254-2620 or [email protected].

“The University of Georgia College of Agricultural & Environmental Sciences is an Equal Opportunity, Affirmative Action, Veteran, Disability Institution.”

Photo Credit 1: Fireplace ashes

University of Georgia Cooperative Extension