I’ve had a number of people over the years ask about using wood ashes in the garden. While they are a source of potassium, ashes are highly alkaline (high pH) – similar, in fact, to household bleach, believe it or not.
We’ve always just added our ashes from heating our home in the winter to our compost pile, which is a slow, “cold” breakdown at our place. Meaning- we don’t mess with our compost- we simply make a pile of house and garden debris, layered with some leaves and shredded paper, and when it gets big we start a new pile and let that one decompose on it’s own over time. We might mix it once or twice, but that’s it.
For those who’d like to add it directly to the garden, or who have more ashes than we do (we don’t heat exclusively with wood), here are some tips and precautions for using wood ashes in the garden:
- Apply recommended amounts to moist soil and rake lightly to mix, remembering to wear protection. Optimal amounts can be determined by a soil test, but usually a 5-gallon pail over 1,000 square feet is considered safe. With ashes, it’s always better to add less rather than more.
- Use ashes from regular wood only- not treated wood or trash, which can contain substances that will inhibit plant growth.
- Don’t use wood ash where potatoes will be planted.
- Since it’s alkaline, don’t spread ashes around acid-loving plants such as blueberries, azaleas, and rhododendrons.
- Always rake or mix ash in – if left in piles, excessive salt from the ash can leach into the soil.
- Also, wait until after seeding to rake ashes in- ash contains too many salts for seedlings.
- For a lawn, wait at least a month after wood ash application before applying nitrogen fertilizer to allow time for the soil to reduce the alkalinity of the ash.
For more information about using ashes in our yards and gardens, visit the OSU Extension Service website.
Do you use ashes in your garden? Do you think they’re helpful or harmful?