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Organic Mulches
Mulching is a practice adaptable to nearly all home gardens. To mulch
is simply to cover the soil around plants with a protective material. Organic
mulches add nutrients and humus to the soil as they decompose, improving
its tilth and moisture-holding capacity.
Most organic mulches should be applied after plants are well
established (4 to 6 inches tall). Cultivate out all weeds before
spreading the mulch evenly over the bare soil between the plants.
Apply organic mulches when there is reasonably good soil moisture
and before the weather turns hot. Infiltration of rain water will
be slowed somewhat by a mulch, so it is best not to mulch over
dry soil. Water thoroughly or wait for a soaking rainfall
before applying any mulch.
Purpose, availability, cost, and final appearance of a mulch are the
determining factors in choosing the type to use. The more commonly used
mulches are evaluated below.
SAWDUST
A 2-inch layer of sawdust provides good weed control. If applied around
growing plants, add 1/2 pound of actual nitrogen per 10 cubic feet of sawdust
to prevent nutrient deficiencies. Fresh sawdust contains a great deal of
carbon and very little nitrogen, and its breakdown requires that microorganisms
take nitrogen from the soil. There is a problem with crusting of fresh
sawdust, with resulting impermeability of rainfall. Sawdust is best used
for garden paths and around permanent plantings. Readily available from
sawmills, it tends to be inexpensive.
BARK AND WOOD CHIPS
A 2- to 3-inch layer of bark provides good weed control, is slow to
decompose, and will stay in place. Shredded bark decomposes more quickly
than chips. Wood chips may be available free or for a small fee from professional
tree pruning services, but many people find them less attractive than bark
chips. Bark chips can be purchased in large bags at retail stores. These
make a very attractive mulch and are especially recommended for mulching
around trees and shrubs.
HAY AND STRAW
A 6- to 8-inch layer of hay or straw provides good annual weed control.
These materials decompose quickly and must be replenished to keep down
weeds. They stay in place and improve the soil as they decay. Avoid hay
that is full of weed seed and brambles. Fresh legume hay, such as alfalfa,
supplies nitrogen as it breaks down. Hay and straw are readily available
in rural areas, but city dwellers may not be able to obtain hay. Straw
can be purchased at most garden centers, often commanding a high price.
Both are recommended for vegetable and fruit plantings.
PINE NEEDLES
Baled pine needles also are found in garden centers. They make an excellent
mulch around shrubs, trees, and in other areas when a long-lasting mulch
is desired. Readily available.
GRASS CLIPPINGS
A 2-inch layer of grass clippings provides good weed control. Build
up the layer gradually, using dry grass. A thick layer of green grass gives
off excessive heat and foul odors rather than decomposing. However, in
limited quantity, clippings decompose rapidly and provide an extra dose
of nitrogen to growing plants, as well as making fine humus. Avoid crabgrass
and grass full of seed heads.
Also, do not use clippings from lawns that have been treated that
season with herbicides or a fertilizer/herbicide combination. Grass
clippings can be used directly as mulch around vegetables and fruit
plants or can be composted. They are an excellent source of nitrogen
to heat up a compost pile, especially for those gardeners without
access to manures.
LEAVES
A layer of leaves, 2 to 3 inches thick after compaction, provides good
annual weed control. Leaves decompose fairly quickly, are easy to obtain,
attractive, and improve the soil once decomposed. To reduce blowing of
dry leaves, allow them to decompose partially. Highly recommended as a
mulch.
PEAT MOSS
A 2- to 3-inch layer of peat moss gives fair to good weed control. However,
peat tends to form a crust if used in layers thick enough to hold down
weeds. It is very difficult to wet and tends to blow away if applied dry.
Peat also is a relatively expensive mulching material.
COMPOST
A 2- to 3-inch layer of compost is a fair weed control. Most compost,
however, provides a good site for weed seeds to grow. It is probably better
used by incorporating into the soil. A layer of compost can be used on
overwintering beds of perennials, such as asparagus or berries, to provide
nutrients and help protect plant crowns.
HULLS AND GROUND CORN COBS
A 2- to 3-inch layer of these materials provides fair weed control,
but both have a tendency to be easily blown by the wind. Peanut hulls stay
in place somewhat better than corn cobs. A heavier mulch, such as partially
rotted hay or straw, can be used on top to hold down the lighter materials.
Recommended if readily available in your area.
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