Mulching

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Why Mulch?
The Truth About Tree Roots
Proper Mulch Technique

Why Mulch?

Mulch helps keep roots cool in summer and warm in winter. It keeps weeds down and helps hold in moisture. A "moat" of mulch also protects urban trees from cuts and nicks caused by lawn-mowers and weed-whippers. Studies have shown that wood-chip mulch can nearly double the rate of tree growth during the few years after planting. Mulch even fertilizes as it breaks down.

The Truth About Tree Roots

To understand the best way to mulch, it's useful to know a little bit about tree root systems. Contrary to popular belief, tree roots do not grow very deep. In fact, 90% of a typical tree's roots are found in the top 12 inches of soil! Roots extend laterally. Think about it: It's much easier to extract water and oxygen (yes, trees absorb oxygen through their roots) from a layer of soil than from the layers of densely-packed clay found further down.

Proper Mulch Technique

Mulch should be spread in a circle as far around the base of a young tree as possible, but at the very least two or three feet out. If there's grass growing around a tree, don't worry about it. A layer of mulch (2" to 3" deep) will kill the grass. It's much, much, much better to let mulch compost the grass naturally rather than risk root damage by digging up the area first.

Mulch should be spread out in the shape of a saucer, not a mound, as is the common mistake. The saucer shape will hold and distribute rain water to a tree's roots more effectively. Mulch mounded up against a tree's trunk can cause bark rot, which makes the tree vulnerable to disease and insect problems, and can kill the tree.