Think Twice Before adding Wood Ash to Your Garden
Think twice before adding wood ash to your garden. It provides minimal benefit with the potential of long-lasting harm to the soil and your plants.
Wood ash does contain significant amounts of potash; the nutrient that supports plant hardiness and disease resistance. Many soils have naturally high to excessive levels of this nutrient or from years of using balanced fertilizers like 10-10-10. Adding more may not be necessary and may interfere with other nutrient uptake.
It provides very little phosphate, no nitrogen and increase the soil pH. High pH soils limit the availability of many plant nutrients including iron, zinc, copper, and manganese. This can lead to iron and manganese chlorosis, a yellowing of the leaves and decline in the plant.
Take a soil test before incorporating wood ash into the garden. And don’t use charcoal briquette ash that can be harmful to your plants.
A bit more information: If your soil is acidic (pH below 7.0) and you decide to use ash as a soil amendment, keep it away from seedlings and plant roots. The University of Iowa recommends applying no more than 20 pounds (about a five-gallon bucket) of wood ash to 1,000 square feet of lawn and gardens in late winter or early spring.