Mulching Trees

    What is that?

    • Mulching refers to the placement of any material on the ground around plants.
    • Mulches can be divided into organic and inorganic materials. The first breaks down over time and becomes part of the soil, the second does not.

    What good is it?

    • There are so many benefits to mulching trees, it is hard to even count them.
    • Almost all mulches make significant contributions.
    protect trunk from mowers conserve soil moisture
    reduce soil erosion impede weed growth
    restrict soil cracking limit salt build-up

    • Most organic mulches add further features.
    protect the roots from traffic
    cut down soil compaction
    improve soil fertililty & structure
    moderate soil temperatures
    • A "green mulch" such as pachysandra or vinca (but not grass) also brings many of these benefits, although it will compete with the tree to some extent for water and nutrients.
    • And, oh yes, all mulch looks good.

    What problems can mulch cause?

    • Except for needing to be renewed now and then, mulches give very few problems.
    • Avoid fresh organic mulches, i.e., those that have not been leached or composted. They often 1) deplete soil nitrogen, especially if small in size and thickly applied, and 2) can be toxic, especially mulch made of conifer (cedar, for example) sawdust and bark.
    • Many mulches, if put on too thick or against the trunk, actually tend to increase disease and insect troubles, especially on poorly drained clay soils.
    • Geotextile fabrics can lead to higher temperatures, and it is hard to get weeds out of them. If you use them, be sure to cut slits for air and water movement.
    • Black plastic and peat moss should be avoided altogether as tree mulch.

    What is the best mulch to use?

    • There is no single best mulch, but organic mulches such as composted bark, branches, and leaves are much better for the tree and often cheaper as well.

    How do you put it on?

    • To the tree’s dripline, if possible. Remember, the dripline moves out as trees grow.
    • No higher than the heel of your hand. Anything from 2-6" will benefit the tree.
    • Not against the trunk. The mulch should look like a donut when you are through.

    Where can I get more information?

    "The Types and Uses of Mulch in the Landscape" (Donald Rakow), available from your local Cooperative Extension or DEC office, and also from the Community Forestry Education Project at 716-461-1000.