Q. About five years ago our HOA -executed a conversion project and
removed the grass, replaced it with rocks. In some grass plots there are some
20 years old pine, ash, olive and privet trees. In order to secure water
supply for these trees, the contractor installed water lines around each tree
in circular formation, and covered them with wood mulch in a radius of
5-6 feet around the trunks. The rest of the areas rocks was placed. Now
the new HOA Board thinks the mulch is unseemly and plans to remove it and replace it withe rocks.I would like to ask your opinion on this.
A. I can understand why HOA members (I’m
assuming the board represents the members) would not like a polkadot pattern of
woodchips with a background of rock mulch in their landscape. That is not my
intent when I recommend woodchips used on the soil surface around some trees.
could look rather odd and decide to cover the area instead with one type of
mulch.
to the soil surface beneath large trees and occupying 5 to 6 foot diameter is
defeating the basic purpose of using woodchips versus rock mulch. If woodchips
are used, they need to be applied to a much larger area under the trees than a
6 foot diameter circle. Their application is meant for soil improvement rather
than aesthetics. The type of mulch selected for landscapes makes a huge impact
on the general texture, “look” and aesthetics of a landscape.
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| Woodchip mulch on top of desert soils combined with water will improve both structure and chemistry enough to improve plant health and growth. You will find the feeder roots growing into this type of soil. |
I’m going to respond to your question in
increments. If this wood mulch is a “bark mulch” rather than a
“woodchip mulch” then its only contribution is aesthetics. Bark mulch
adds very little to soil improvement. Its use is almost 100% aesthetic. Using
bark mulch has its pluses and minuses but on the minus side it does very little
to improve the soil and so it is quite similar to rock mulch in that regard.
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| Large decorative bark mulch is used for aesthetics and not soil improvement. Photo courtesy Viragrow Inc. www.viragrow.com |
bark mulch or rock mulch in that its primary use is long-term and its focus is
on soil improvement. It’s very handy, and I would argue irreplaceable, for some
trees when changing a landscape from lawns to “desert”, a.k.a. rock
mulch landscapes.
plants. The one tree on your list you will have problems with is the Japanese
Privet. This tree will be very tricky for it to look good in a landscape covered
in rock mulch. Actually, it may have trouble growing well even in woodchip
mulch because the problem is soil moisture rather than soil improvement.
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| Japanese privet looking its best in a rock landscape. |
In our
desert climate, JP looks good in a lawn where the soil is moist continuously
and small amounts of organics are added back to the soil each year. This
happens just by having the lawn growing around it. When the lawn is removed, it
starts to suffer. I would be surprised if it looks good even after the first
couple of years in a rock mulch conversion from a lawn. This tree definitely
will have trouble growing well in a rock landscape. Depending on which ash
tree, this is another tree that may struggle growing in soil covered 100% by
rock.
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| Most ash trees grow better in lawns than in rock mulch. |
problems with pine or olive trees growing in soil covered by rock. They will
need fertilizer applications now that the lawn is gone. A suggestion, use a
very coarse rock (1 inch or larger) of the same color under these trees when
replacing the wood mulch. Then add compost underneath the canopies of these
trees growing in coarse rock mulch every one to two years and water it
in. If you use a “rich compost” such as Viragrow’s, you can skip annual
fertilizer applications and save a little bit of money.