Here in Maine the rain can be acidic. Power plants and other coal-burning enterprises in the Mid-West and South produce sulfur that mixes in the clouds to form sulfuric acid which then drops on us. The rain is not so caustic that it burns holes in things, but the lower pH makes a noticeable difference in the soils and waters of our state. To combat the acidification, we farmers must sweeten the soil by raising the pH so certain plants will grow better.
Some plants love low pH: blueberries, azaleas, rhododendrons, all thrive on more acidic soil so don’t sweeten around those plants. Many garden plants and trees need soils closer to neutral pH and in this area require soil amendment to do well. The primary additive for raising soil pH is lime. Finely ground or pelleted, farmers and gardeners spread this mineral liberally. Lime can get expensive, especially if there are large areas needing attention. Here at Phoenix Farm we have a free neutralizer: wood ash.
Our efficient, low emission, wood burning stove heats the whole house all winter and produces a plentiful supply of ash. Ash is the powdery, whitish-gray residue of wood burning, not the black chunks that are coals of incompletely combusted wood. Wood ash is a very potent pH neutralizer. The alkaline properties of ash were discovered thousands of years ago when people first learned to extract lye from the ashes of their cook fires. Ashes are more efficient at neutralizing than lime and are spread more thinly on the soil.
My pear trees are an example of the power of wood ash. For years they bloomed and did not fruit. Pears require boron in the soil to set fruit so I added borax around the bases with limited results. Then I learned that too much acid in the soil can damper fruit set. I spread wood ash around the bases of the trees during the winter and as soon as that following spring, the fruiting improved. Now, several years later, the trees produce copious harvests, more than we can use!
I’ve spread wood ash on grass areas where moss is trying to take over. If moss is allowed to grow, the built-up layers of dead moss will leach more acid into the soil until only moss and other acid-loving plants will grow there. The wood ash effectively ruins the soil for moss, killing it and encouraging grass to grow. I have greatly improved places in the lawn and pastures where moss was trying to take over.
Lilacs, fruit trees, grapes and most garden plants benefit from wood ash application to the soil. I’ve found that the best time to apply the ash is in the winter. The snow catches the powdery ash and prevents it from blowing away. At the spring thaw, the ash causes snow to melt more quickly. The ashes rapidly settle onto and then into the ground.
An example of the power of higher soil pH in the garden is my experience with tomatoes. When I began gardening, the tomatoes I got were very acidic tasting, so strong that they were nearly unpalatable. The next year I added lime in the holes dug for the transplanted tomato seedlings. The tomatoes grew better and their fruit was sweet and tasty, the way it should be. To keep the garden pH up, I broadcast wood ash over the plot in the winter. The ashes improve my tomatoes, corn, beets, carrots and squashes and cause the snow to melt more rapidly in the area, warming the soil sooner for earlier planting.
So, don’t throw those wood ashes away. If you burn wood, save the ashes and use them yourself or give them to local farmers and gardeners. Wood ash is not trash, it is a valuable commodity.