Burning Oak Leaves

Asked March 12, 2020, 5:49 PM EDT

For the past few years I've been raking oak leaves onto my vegetable garden and then burning them -- once in the fall and again in the spring. Is this bad for a vegetable garden? I had the soil tested -- it is loam and I was told I need to add sulfur to acidify (it's at 8 now) also, that I have an above optimum level of magnesium. My garden been going downhill for the past few years and I wonder if it's because of the leaves.

Livingston County Michigan

1 Response

Wood ash is known to raise the pH of soil and I could only find one source that mentions that the same thing happens when burning leaves. A pH of 8 is high for most plants and at this point I would avoid any ash in the garden. The leaves can add great organic matter back to the garden soil and release nutrients that would greatly benefit the soil and in turn the plants. This does not happen when they are burned. Use a lawn mower to grind leaves in the lawn and pick them up. These chopped of grass and leaves can be spread across the garden and flower beds. Worms and other organisms will feed on the grass and leaves and this valuable material is spread by the worms through the soil. As soil pH goes up to levels of 8 you will see a decrease in plant productivity. Recycle the leaves. Burning may release nutrients but it does not improve the soils structure and ability to hold water and nutrients.