This is just as true for
a tree when you are talking about mulching. Mulch is good. Mulch
is almost always good for the soil in our gardens. It keeps the
surface cool, discourages weed growth and, if we are talking chips
or eucalyptus mulch (or compost or recovered wood products), gradually
breaks down to improve the soil.
But how you use it makes
a difference. We are realizing with more and more certainty that
planting depth is a major factor in whether a tree lives or dies.
Roots emerge at the base of the trunk: the top of this region from
which the roots emerge should be just at ground level when a tree
is planted. You must always check this, and cannot even trust the
older idea of planting it at the same level that it was in at the
nursery. Sometimes a tree will come to you already too deep in the
pot, and will need to have a little soil removed to have the main
roots just showing.
However, it is no good
planting at the right depth and then covering the trunk base with
thick mulch. The roots of a tree have evolved to be underground:
mulch over them is fine, and here is where the doughnut shape comes
into play. A nice two or three-inch depth of a good mulch is great
over the whole soil surface around a tree, except that it must not
touch the trunk. Do your mulching leaving a few inches out from
the trunk as the hole in the doughnut: dust this open space with
a little mulch to get the uniformity of color if you wish.
The trunk of a tree requires
the drier atmosphere of the open air, and mulch piled high on the
base in a volcano shape can cause rot and sometimes root growth
where you don't want it.
Volcanoes are bad, doughnuts
are good. If only all of life's questions were as easily resolved.
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