Warm fires in the fireplace and glowing wood stoves really take the chill out of the air, but it always brings up the question of what to do with the ashes. Those of us who like to smoke meat over wood fires face the same problem throughout the year.
Adding leftover wood ashes to the compost bin or pile is your best bet for reuse. Compost is typically a little acidic and the ashes will help to neutralize it.
The bad news about adding wood ashes to the garden is that the addition may raise the pH of the soil. With soil pH well above neutral in many gardens in the county, you should never assume that the ashes make a good soil amendment.
A quick lesson on soil pH: most plants prefer a pH between 6 and 7 (slightly acidic). This range is favorable to most soil microorganisms, which work to break down organic matter for the plants’ use. Nutrients are also more available to the plant. There are some exceptions – blueberries prefer very acidic soil, and some plants, like fescue turf, can tolerate a very wide pH range.
In other parts of the country, you might be able to safely assume that your soil is acidic, but pH varies widely across northeast Kansas.
I also get asked about the nutrient content of wood ashes from people who suspect there may be value as a fertilizer. Assuming your soil was acidic, you could use wood ashes to add potassium, phosphorus, and trace elements to the soil. Nutrient values vary with the type of wood, but on average, ashes are about 1.5 percent phosphorus and anywhere from 1 to 10 percent potassium.
Supposedly, old-timers tossed ashes through their trees in the mornings to control insect and disease problems. There are still some gardeners around who sprinkle ashes on their shrubs and flowers with the same idea in mind. This may work for insects that prefer climbing over smooth textures rather than gritty ash-covered ones, such as slugs, but too much could cause more harm than good.
The only other option I have is saving all your ashes for spring soap-making. This method takes a sense of adventure and a penchant for soft lye soap, but was one way that early settlers recycled.
If you must dispose of the ashes in the landfill, let them cool for several days before bagging tightly and setting out with your regular trash pickup.
Charcoal briquettes often contain a binding agent that is toxic to plants. Ashes from briquettes should not be used in the garden or the compost bin.
Jennifer Smith is the Douglas County Extension Agent – Horticulture for K-State Research and Extension. She can be reached at 843-7058.