How to Use Ashes As Fertilizer

Use wood ashes as a soil amendment in the early spring while the soil is dry and before the plant life has begun to actively grow. Nearly all plants benefit from the potash content of wood ashes. Other components of the ashes are beneficial to the soil and plant growth as well. Because the wood ashes act as a liming agent, they reduce the acidity of the soil. Plants that prefer acidic soil such as blueberries, azaleas or rhododendrons will not thrive if wood ashes are applied.

Apply 20 pounds (9 kg) of wood ashes per 1000 square feet (93 square m) of soil, tilling them thoroughly into the soil. Leaving the ashes in concentrated piles could cause too much of a salt build-up in areas of the soil that could potentially harm your plants.

Sprinkle ashes upon each layer of your compost pile. The ashes help break down the organic materials as they compost.

Amend heavy clay soil by using wood ashes because they break up the soil and help it retain more air.

Deter garden pests by using wood ashes. Sprinkled lightly throughout the garden bed, wood ashes repel maggots, aphids, slugs, snails, and cutworms. Reapply the ashes after heavy rains.

To keep your ashes where you want them, apply them on a day that is not too windy. Otherwise they're liable to blow away before they have a chance to settle into the soil.

Use caution when using ashes in the garden. The ashes contain a good amount of lye which is a caustic agent. For this reason, refrain from placing them on young tender plants. Wear gloves when handling the ashes. Use a mask to avoid breathing in the residue and protect your eyes with sunglasses or goggles. Avoid using ashes from cardboard, coal or painted wood. These substances contain chemicals that can be harmful to your plants. Monitor your soil to be sure it hasn't become too alkaline. Use a soil testing kit to check the PH levels or take a soil sample to your county extension office lab to be evaluated. Alkaline soil will need sulfur added to it.

Produce more wood ashes by burning hardwoods rather than soft woods. Hardwoods will make 3 times the amount of ash per cord of wood than soft woods.