How to Fertilize Plants with Ashes

The potassium in wood ashes encourages strong stems in plants while the phosphorus in the ashes encourages root growth. Soils low in potassium often benefits from wood ash but be careful with acid-loving plants such as blueberries, rhododendrons and azaleas. To use wood ash safely, add a small amount to your compost pile. Here the wood ash will help maintain a neutral condition, which is the best environment to help microorganisms break down organic materials. Sprinkle ashes on each layer of compost as the pile is built up and allow the ash to dissolve in the compost. Also, be sure not to use any pressure-treated wood ashes.