Brown compost is the original earth-friendly mulch. The raw materials of brown compost are organic materials high in carbon: leaves, twigs, and other woody wastes like sawdust and wood chips. These can usually be used as mulch in your landscape without further composting. Brown compost can also be mixed, in a composter or compost pile, with high-nitrogen organic wastes (“greens”). The proper mixture of browns with greens speeds decomposition and ultimately results in an ideal soil amendment: dark, earthy-smelling, finished compost.
Fall brings a surplus of leaves, the most common brown compost material from the yardscape. Shredding leaves during or after collection can make moving leaves much easier. A simple way to shred leaves is to simply go over them with a lawnmower. Avoid over-shredding the leaves; leaves shredded too finely produce mulch that will compact and not allow water to penetrate the soil. Lawn tools like the Cyclone Rake, a leaf and lawn vacuum pulled behind a riding lawnmower, make it much easier to collect and deposit shredded leaves wherever you want them.
Shredding leaves is also important for using them to make compost for amending soil. Shredded leaves have more surface area for aerobic bacteria to decompose, an advantage in the composter or compost pile. Shredding or chipping other brown compost materials, like sticks, results in a less bulky product for the compost pile as well as a more uniform material for mulching.
A layer of two or three inches of shredded leaves is a good thickness for mulch. Leaves work well when mulching around established plantings; freshly shredded leaves worked into loose garden soil can tie up soil nitrogen as the leaf continues decomposing. Some leaves, like oak and beech, may make the soil more acidic – so use those leaves around plants that are tolerant of acidic soils.