Burning Wood This Winter? Here's How To Use The Ashes To Help Your Garden

If you've been burning wood for warmth this winter, you probably have some leftover wood ash.

Gardeners can use the nutritional value of this ash in their landscape. Since wood ash is derived from plant materials, it contains many nutrients that plants need to survive.

When wood is burned, gases such as nitrogen and sulfur are released, and other nutrients remain as trace elements. The actual fertilizing value of your ash depends on the type of wood you burn. Ash from hardwoods such as oak generally contains more nutrients than ash from softwoods such as pine.

In general, hardwoods produce three times more ash and five times more nutrients per cord than softwoods. In other words, oak ash can meet the potassium needs of a 60-by-70-foot garden and contains enough calcium and magnesium to reduce soil acidity with a slight increase in soil pH.

Compared to the energy neutrality of traditional lime, wood ash is less efficient per pound of product; However, because it contains so many water-soluble nutrients, studies show that it can increase plant growth by up to 45% compared to traditional limestone.

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Each pound of wood ash is equivalent to one-third to one-half kilogram of agricultural limestone. Under normal conditions, 5 to 10 pounds of wood ash per 100 square yards will neutralize excess soil acid and raise the soil pH to a favorable level.

This ash liming is important because over time it helps to improve soil structure, making garden areas more airy and easier to maintain.

Soils with low organic matter, soils that require lime, and hard soils in particularly dry conditions are ideal for using wood ash. Wood ash can be used effectively in the following cases:

When the soil is acidic and low in potassium, it is good for most garden plants except acid-loving plants such as wood ash, blueberries, rhododendrons and azaleas. Use wood ash in flower beds, lawns and shrub beds.
One and a half to one kilogram of wood ash per year is recommended for each bush and rose bush. Sprinkle the ash evenly on the soil around the perennial. Lightly sprinkle the ashes on the soil, being careful not to damage the roots. Never leave ashes in piles or piles, because if they pile up together, too much salt will seep into the soil and create an unhealthy environment for plants.
Lawns that require lime and potassium can also benefit from wood ash. Apply no more than 10 to 15 pounds of ash per 1,000 square feet of lawn, as high ash levels make the soil less conducive to plant growth. Do not use fly ash when soil pH is above 7.0.
Wood ash can be used in your compost pile to maintain a neutral and optimal environment for microorganisms that help break down organic matter. As soon as the pile is formed, sprinkle ash over each layer of compost. The ash will add nutrients to your compost.

In addition to improving soil structure, adding calcium from ash can also be beneficial in eliminating plant nutrient problems such as rotting tomatoes and peppers. Although ash can be applied at any time of the year, fall is ideal as the soil overwinters to adjust its pH before planting in the spring. Do not apply ash before planting or early germination, as this can create short-term concentrated alkaline conditions that can stunt plant growth.

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Despite all the benefits of adding wood ash to your garden, you still need to schedule a soil test to determine if liming is necessary. A soil test will give you an idea of how much wood ash might be suitable for your garden area. Not all plants benefit from wood ash. They should not be used on acid-loving plants such as blueberries or azaleas. Other garden crops such as beans, blackberries, potatoes and strawberries should only be treated with wood ash when a soil test shows the soil pH has dropped below 5.6.

Wood ash contains elements that cause environmental problems. However, care should be taken to prevent ash from falling into surface and ground water.

Also, avoid applying ash right after or before a heavy rain.

Since ash is an alkaline material, it can cause skin irritation. Wear long sleeves, gloves and a dust mask when applying.

It's also important to remember that fresh ash may still contain hot coals, which pose both a health and fire hazard.

Finally, don't throw away those ashes. Use them properly in your garden and landscape.

Mr Andrew Rideout is UK's Horticulturist and can be contacted at pandrewrideout@uky.edu.

This article originally appeared in the Henderson Gleaner: Burning wood this winter? Here's how to use ash to help your garden