By Calvin Finch, Ph.D.
Mulch is an essential part
of gardening in South Texas. There is a long list of benefits
to the practice of mulching. Saving water leads the list.
When we think of mulch we usually
think of organic material like bark or shredded brush but mulch
can be any material that covers the soil to reduce evaporation
and reduce weeds. Plastic is used quite often in agricultural
fields and examples of rock mulches exist in every urban neighborhood.
Something that we often overlook as a mulch-like option in our
landscape is pervious hardscape.
Flagstone, brick without mortar,
and treated wood sidewalks and patios are almost as beneficial
as organic mulches over the roots of established live oak trees.
You can protect the trees from compaction and still have a usable
surface for human activities. Use flagstone, patio blocks and
brick without mortar placed into 2-4 inches of sand with a treated
wood border, and you have a mulch that protects the roots from
compaction, lets water penetrate and allows gases to escape.
As good as inorganic mulches
can be for some situations, we usually think the best mulches
are organic. They mimic the natural process in the prairies
and forests where layers of organic material enrich and insulate
the soil as time passes. In the North where cold weather slows
the rotting process, the organic material accumulates. Here
in the South we are like one big compost pile, and the organic
material does not accumulate in the long term.
Mulch saves water by insulating
the soil. Mulch also keeps the soil cool. The summer sun beating
down on bare soil heats it to temperatures so high that root
growth does not exist in the upper 2 inches of the soil. When
we only have 4-6 inches of soil we cannot afford to lose the
top 2 inches. Organic mulches usually will not eliminate all
weeds, but they certainly reduce weed pressure and make them
easier to remove.
The best mulch is the one that
is the most available. We cannot afford to waste any mulches.
Leaves are great because they
are available in the fall when the deciduous trees drop their
leaves and then again in March when the live oak leaves fall.
I don't know who ever started the rumor that pecan and oak leaves
were not good for mulch because of acidity, but they were wrong;
use them in your vegetable garden or shrub border. It is a real
sacrilege to send leaves to the landfill with the garbage pickup.
We waste the organic material, pay to have them hauled away
and then waste valuable landfill space.
City of San Antonio residents
can get free shredded brush mulch at the 1800 Bitters brush
collection site, 7days a week. You have to load it yourself,
but the material is excellent for placement over newly planted
tree roots and in the shrub border. Three to four inches of
mulch over the roots of a newly planted tree increased growth
rate by about 40 percent when compared with trees where sod
grew up to the trunk.
Bark mulches and cypress mulch
are particularly decorative. I like cocoa shell mulch for containers
and small beds. It is fine enough that it does not overwhelm
small plants. Pecan shells are seasonally available in large
quantities. They work fine as long as you do not want to walk
barefoot in your mulched beds! Shredded cedar that has leached
for a season can be used as thick as you want for mulch.
Compost is a great mulch but
is most valuable as a soil enricher. If you use compost as a
mulch, cover it with a coarser material like bark or shredded
brush to keep weed seeds from germinating and the material from
Your favorite nursery has bags
of mulch. In large quantities, or for more variety, visit Gardenville,
Fertile Garden Supply, Living Earth Technology, Keller Material
and other suppliers.