Park and cemetery trees in areas
of low foot traffic tend to have
the good life, roots-wise.
not only grow horizontally beyond the dripline (the
canopy edge), there is often a higher percentage of
them beyond the dripline than within it. (This is why
those orange plastic 6-× 6-foot protection zones around
trees on construction sites are woefully inadequate.)
Tree roots are found primarily in the top 12 inches of
soil. The reason for this is that oxygen becomes lim-
iting the further down you go through the soil profile.
Tiny absorbing roots, responsible for most of the tree's
intake of water and nutrients—and therefore criti-
cally important—are in the top few inches of soil, right
under your feet. The finer the roots, the greater the
surface area through which water can enter by osmosis,
which is why conservation of fine roots matters.
What can you do to protect a tree's root system?
Don't mulch too deeply. Maintain a depth of about
3 inches of bark mulch, but no more, or else fine
feeder roots lose their ability to "breathe"—i.e.,
exchange gaseous oxygen and carbon dioxide.
Mulch as far out as you can. Because those critical
fine feeder roots are so close to the surface, the roots
of lawn grasses will be in direct competition for water
and nutrients unless you favor the tree. To do this, give
your tree as big a mulched bed as possible—at least to
the canopy edge and ideally, beyond. But remember,
mulch should be no more than about 3 inches deep. >>
Park and cemetery trees in areas of low foot traffic tend to have the good life, roots-wise.
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