Every spring we make new leaf mold. This is part of this year’s huge pile of ground-up leaves… by next spring it will have become a pile of rich black “soil” that will do wonderful things to our gardens. This year we will be spreading last year’s gigantic pile of leaf mold around all the hostas as we clean out each garden. Incredibly, despite the huge size of these piles, we could always use more.
Almost all of the trees surrounding the areas we rake are maples, so maple leaves are the main component in the leaf mold we make. We used to use the wood chipper to grind up the leaves, but now we prefer to use a “dedicated” lawn mower. We don’t add anything to the leaves, but they will naturally contain some pine needles and pieces of grass and other vegetation that get caught up in the raking. These all help the pile to heat up. We build each pile layer by layer as we rake and grind the leaves, and we always moisten each layer thoroughly before adding more ground leaves. The leaves must be damp or the pile will not heat up quickly, but if the leaves are too wet, the pile will probably not heat up at all. With practice it becomes very easy to find the right balance.
This new pile is just starting to heat up now. Four days ago the temperature inside the pile was in the 40’s (it’s been cold here!). The next day the temperature had gone up to just over 90°F and continued to rise. This morning the thermometer is registering at just slightly under 130°F. Usually this type of pile will achieve and hold fairly steady temperatures of around 140°F before slowly cooling down again.
Many of you have asked me about the thermometer we use… it has a twenty-inch probe that goes down into the pile. We’ve had this one for a while, but they are readily available in any garden center and cost approximately thirty dollars. A thermometer isn’t really necessary to make good leaf mold, but it is interesting to be able to see verification that the pile is heating up… also, knowing the temperature is a big help in monitoring the pile’s progress.
The work on the pile in this photograph is done now… we will not have to do anything more to it until we use the leaf mold next spring.