Compost is that rare thing that is nearly incontestably good, and there’s a good reason why gardeners alike refer to it as “black gold.”
The inclusion of compost in your yard hosts a myriad of benefits on a small and surprisingly large scale:
On a small scale, compost acts as a soil-enriching amendment that 1) reduces the need for chemical fertilizers, 2) increases soil fertility and its ability to retain water (thus reducing the risk of erosion), and 3) provides valuable nutrients for your plants while also suppressing diseases.
On a more macro scale, composting collectively reduces our carbon footprint by 1) reducing the amount of trash that ends up in our landfills, 2) reducing the number of pesticides and fertilizers we use (which require fossil fuels to produce and are potentially harmful to consume).
It’s a pivotal time in the composting world because those nutrient-rich leaves—a fabulous addition to your compost—are on the verge of falling. However, in the composting world, not all leaves are created equal. While most leaves will enhance compost with beneficial nutrients when they break down, others can slow the decomposition process and harm your plants when incorporated into your garden.
What makes a leaf good or bad for compost depends on its levels of lignin. In the composting world the lower the lignin, the better.
So, what is lignin, anyway?
Think of lignin as a polymer found in the tissues and cell walls of plants. It plays a vital role in transporting water and removing waste in plants and trees. Lignin gives plants, trees, and leaves that “woody” texture, and is the thing responsible for that satisfying crunch when you bite into veggies, like, say, a carrot or a green bean.
But leaves with extremely high lignin levels can have adverse effects on your compost. For one, high lignin levels are usually associated with thicker and woodier leaves, which means they take a long time (sometimes years) to break down. Likewise, leaves high in lignin will steal the nitrogen away from your compost mix needed to make your plants happy. A good, easy rule of thumb is the thicker and woodier the leaves, the higher in lignin they are, and the worse they are for your compost.
Some good leaves for compost = cherry, willow, elm, ash, fruit trees, and poplar.
Some bad leaves for compost are beech, oak, ginkgo, eucalyptus, and black walnut.
So, how can you prepare? Create a plan!
1) Understand what kind of trees you have. Use a tree identification book or app to help.
2) Compile good compost leaves and bad compost leaves separately. Dispose of bad compost leaves in their own pile, and keep in mind that leaves like beech and oak can often take a few years to decompose, depending on climate.
3) For maximum results and speedier decomposition time, shred your leaves before putting them in compost. If you have a lawn vacuum, this will do the job for you! If you don’t, you can do this by putting the leaves in a sturdy trash can and shredding them with a weed whacker.
Best of luck with your black gold endeavors!