B. Dean McCraw
Texas Agricultural Extension Service
Mulching your garden shows you really care about
your plants. A mulch is any substance spread on the ground to
protect plant roots from heat, cold or drought or to keep fruit
Mulching is a long established horticultural
practice. Farmers know that shallow cultivation of the soil's
surface after a rain slows the rate of water loss from the soil.
The shallow layer of dry surface soil acts as a mulch.
Mulches can be classified as inorganic or organic.
Inorganic mulches include plastic, rocks, rock chips and other
non-plant materials; whereas, organic mulches include straw,
compost, sawdust and similar materials. Plastic is the only
inorganic mulch used in vegetable gardens.
Value of Mulches
A thin layer of mulch on the soil surface (especially
in sloping gardens) reduces the washing away of soil particles
by rushing water. Also, mulches prevent raindrops from splashing
on the soil surface. See figure 1.
Saving soil moisture is an important use of mulch
in Texas. A mulch layer on the soil surface allows the soil
to soak up more water. Mulch also reduces the rate of water
loss from the soil. A 3-inch layer of mulch on the soil surface
dries much faster than the soil below it. Thus it prevents water
from moving into the air. See figure 2.
Mulches modify soil temperature in home gardens.
Applied in late fall, winter mulch insulates plant roots, crowns
and stems of winter crops from extremely low temperatures.
mulching in summer months keeps the soil cooler. Soil covered
by black or clear plastic or dark organic mulch in early spring
warms faster than bare soil. This allows earlier planting
of warm-season crops. See figure 3.
Use light-colored paper such as newspaper in
summer to keep the soil cooler. Organic mulches such as compost
and sawdust also keep soil below the mulch layer cooler in
summer. Dark soil warms much faster than light-colored soil.
See figure 4.
Organic mulches enrich the soil as they decay and provide
a better environment for plant growth. Soils high in organic
matter are easier to till and better suited to vegetable gardening.
Adding organic material makes soils more crumbly, especially
clay soils that pack and crust.
Mulches help plants by gradually increasing
soil fertility. An organic mulch such as straw or newspaper
can be turned under the soil at the end of the season. This
helps build the soil's organic matter content. Turn the mulch
under as soon as the gardening season is over so it breaks
down before the garden is replanted.
Most mulches also provide excellent weed control.
Mulches do not prevent weed seeds from sprouting. However,
weed seedling emergence is blocked by a mulch layer thick
enough to exclude light. A 3-inch layer of mulch on the soil
surface keeps most annual weed seedlings from coming through.
See figure 5. Weeds that bread through are removed more easily
from mulched soil. Hard-to-control weeds such as nutgrass
and johnsongrass may come through the mulch layer but can
be pulled more easily or covered by fluffing the mulch with
A well-mulched garden can yield 50 percent
more than an unmulched garden the same size. Space rows
closer as there is little or no need to cultivate the soil.
Plant food is more available in cooler soil, and the extra
soil moisture increases plant growth and yields. You will
harvest more fruit because of less fruit rot. Fruit does
not touch the soil, and soil is not splashed up on the fruit.
See figure 6. This is true for tomato fruits that rot easily
when resting on the soil surface. Potatoes can be mulched
heavily as the vines grow. This causes tubers to form in
and under the mulch layer. These potatoes are less susceptible
to soil rot, easier to harvest and less likely to be bruised
Garden mulching reduces maintenance. A good
mulch layer eliminates the need for weeding, and mulched
vegetables are cleaner at harvest time. Fruits of tomato,
melon and squash plants never touch the soil.
Many materials are available for mulching
a garden. Some examples are: compost, straw, gin trash and
- Compost is generally the best mulching material
for the home garden. It is usually free of weed seeds
and is inexpensive. Prepare compost from materials present
in your yard. It is not necessary to purchase expensive
materials for mulching.
- Straw is short lived and coarse textured. More
straw is needed for the same effect as compost or lawn
clippings. Generally, less of the finer-textured materials
is required to provide a 3-inch layer of mulch after
settling. compost, however, usually requires only about
4 inches to provide a 3-inch mulch layer.
- Gin trash is commonly available in Texas. It
is risky to use, however, without knowing its source
and prior treatment. Make sure that the farmer did not
use arsenicals on the cotton. Arsenicals are long-lived
chemicals that can be present in gin trash for several
months or years. Also, gin trash may contain weed seeds
and diseases. Compost gin trash before applying it to
your garden to make it safer and easier to use. The
heat generated by composting kills most weed seeds and
most disease organisms that infect plants.
- Sawdust is commonly available especially in
East Texas. If well managed, it can be a good mulch.
It can result in a temporary, but sharp, decrease in
soil nitrogen. Add a small amount of garden fertilizer
to the soil after applying sawdust directly to a garden.
Even better, add nitrogen to sawdust, then compost it
before spreading it on your garden.
- Plastic is an effective mulch if used properly.
Use black plastic in the spring and early summer to
warm the soil. Black plastic keeps light from the soil
and prevents weeds from growing. Clear plastic warms
the soil, but weeds can grow beneath the plastic. A
disadvantage of plastic is that it cannot be turned
into the soil at the end of the season. See figure 7.
Selection of Mulching Material
When selecting materials, consider these factors:
- Cost of the material. Do not spend money
on mulching material when suitable materials are available
at little or no cost.
- The crop you plan to much. Never use material
from the crop that is to be protected. For example,
do not use potato vines from the spring crop to mulch
fall potatoes for the possibility of disease is increased.
- When the mulch is to be used. Select a light-colored
mulch during the summer and early fall to reflect
heat. Use a dark-colored mulch in early spring to
help warm the soil to permit earlier planting and
hasten early growth.
Spread mulches on freshly cultivated, weed-free soil
before plants are large enough to interfere. Apply organic
mulch thick enough to leave a 3-inch layer after settling.
Four inches of fine materials like compost should be
adequate. Remember that coarser materials, such as straw,
settle and may require 6 inches or more initially. If
you use newspaper, place three layers on each side of
the row. see figure 8. Add more mulch during the season
if you are working with organic materials. The mulch
settles and gradually rots during the growing season
where it meets the moist soil surface. Adding additional
layers assures continuous weed control, a clean resting
place for the fruits of your labor and creates a pleasing
appearance all season long.
Hypertext markup and graphics colorization by Gretchen
Eagle and Dan Lineberger.