How to Use Wood Ashes in the Garden

If you are burning wood for heat you may have wondered what to do with the abundance of ashes left over in your woodstove or fireplace. One cord of wood, after all, will yield plenty of ashes – approximately 20 pounds of it, or enough to fill one 5-gallon pail.

Add Wood Ashes to the Garden, but Not Too Much

One of the uses for woodstove ashes is to scatter it in your soil. It is particularly good for acidic soils since it raises the pH (or alkalinity) of the soil, much like limestone (the ideal pH for garden soil is between 6.5 and 7.0). If you don’t know the pH of your soil, make sure you have it tested before applying wood ash.

The University of Georgia Extension Service notes that ash from good quality hardwood contains a healthy dose of potassium (also known as potash) which is essential to healthy plant growth. It also contains more than 13 essential nutrients the soil needs for plant growth. Add wood ashes to flower beds, lawns and shrubs – but keep it away from acid-loving plants (that need a soil pH of 4 to 5.5 range) such as blueberries, rhododendrons, azaleas, mums, oak, and mountain laurel, for example.

But too much of a good thing is actually bad for the soil. Wood ashes are much more water soluble than limestone and changes the pH of the soil quite dramatically in a very short time. A too-high pH can interfere with the uptake of nutrients by a plant.

Safe Application of Wood Ash to the Garden

The University of New Hampshire’s Cooperative Extension recommends the following steps for safely removing and storing wood ashes:

1. Remove wood ashes from woodstove or fireplace according to the manufacturer’s directions.
2. Store wood ashes in a covered metal container on a cement floor or bare ground at least three feet in all directions from any combustible surface.
3. Don’t store the ashes inside the house or on a wooden deck or porch.
4. Make sure the ashes are cold before using them in the garden.

Safe Rate of Wood Ash Application

The best time to spread wood ash is in the fall, but you can apply it over the winter as you empty out your woodstove or fireplace. Do not dump ashes in piles in one spot in the garden soil since it will cause excessive salt to leach from the ash into the soil – a toxic environment for plants.

Broadcast the wood ash in different parts of your landscape (make sure you use gloves since it is a strong alkaline substance). A safe rate for wood ash distribution is 20 pounds (or a 5-gallon pail) per 1000 square feet of landscape. When you add the appropriate amounts of wood ashes to your garden, flowers or grass, there will be no need for additional applications of lime in the spring.