MULCHING BASICS
This page
discusses the importance of mulching, especially in our warmer Gulf Coast
environments and provides a comparison chart of various materials used for
mulching purposes. First, some basics. Why mulch??
1. Water
retention - mulching plants is an effective way to hold available moisture in
the root zone which in turn helps in conserving water and reduces the amount and
frequency of necessary watering.
2. Moderation of
soil temperature - keeps soil cooler in summer and warmer in winter to help
avoid extremes in soil temperature change.
3. Weed growth
prevention - reduces frequency of weeding and when weeds sprout , makes it
easier to pull them.
4. Soil
Conditioning - prevents erosion or soil compaction. Decayed organic mulches
add to soil nutrients and help acidify soil pH.
5. Appearance -
mulching provides an attractive, finished look to any landscaped area and often
provides a background to display plant features.
Organic mulches
should be applied to 2 - 4 inch depths, not be placed right against woody plant
or tree trunks and will need to be periodically replaced.
Do not limit
mulching to just around individual plants. Mulch entire bedding areas in order
to achieve all the benefits of mulching.
Mulches should be
avoided around plants that require dry soil conditions. The general guide is to
think about the environmental conditions where the plant is native or naturally
grows.
The following
table provides information about various types of mulches.
| ORGANIC |
Best Depth |
Advantages |
Disadvantages |
| Ground Hardwood* |
2 - 4 inches |
binds soil; lets water in; holds
moisture; moderate rate of decomposition |
Expensive; may compact; thin layers
are unattractive |
| Shredded Bark* |
3 - 4 inches |
binds soil; lets water in; holds
moisture; slows rate of decomposition |
Expensive; may compact; thin layers
are unattractive |
| Wood Chips |
3 - 4 inches |
Lets water in; holds moisture; cools
and seals the soil |
decomposes rapidly: robs soil of
nitrogen |
| Chipper Debris |
3 - 4 inches |
shredded bark, leaves, etc, available
from tree trimming services, free or cheap |
Mixture of materials results in uneven
appearance. |
| Sawdust and wood shavings |
1 - 3 inches |
decomposes adding humus to soil; free
of weed seed; improves water holding capacity |
robs soil of nitrogen; can hold a lot
of water; increases weight of mulch; can damage tender plants. |
| Pine needles* |
2 - 3 inches |
increases water holding capacity;
decomposes rapidly adding humus and increasing acidity to soil. |
short lived; settles and may decrease
water penetration ability. |
| Lawn Clippings |
1 inch at a time |
readily available, lets in water,
holds some moisture |
can convey toxic "weed and feed"
chemicals from treated lawns. |
| Leaves |
2 - 4 inches |
holds the soil; lets water in; good
for trees and shrubs |
harbors insects, diseases, and weed
seeds; robs soils of nitrogen |
| INORGANIC |
|
|
|
| Plastic film |
3 - 10 mm |
holds water very effectively: controls
weeds |
must be covered with another material,
heat can build up |
| Woven fabric* |
3 - 10 mm |
excludes weed effectively. allows good
water penetration |
expensive; must be covered with
another material |
| Gravel, River rock |
1 - 3 inches |
lets water in; holds no water itself
but keeps it in soil; variety of colors |
expensive; labor intensive to install,
some weeds can still penetrate it. |
| Crushed stone |
1 - 3 inches |
lets water in but holds none itself;
keeps water in soil; variety of colors |
expensive; labor intensive to install;
can be too reflective if white. |
* These are the best all around choices
in our opinion.
Mulch can be purchased by 40 lb bags or
delivered by the cu. yd. Bagged mulches make sense for small areas and are
measured in cu. ft. For large areas, it is more economical to order mulch by
truckload in cu. yds. To determine how much you need. - do the math. As an
example, if your total area to be mulched is 100 ft. long by 10 ft. wide, and
you want to place 3" of mulch on it, multiply 100 x 10 = 1,000 sq ft. 3" =
.25 ft, so 1,000 sq. ft x .25 = 250 cu. ft. There are 27 cu. ft in a cu. yd,
so 250 / 27 = 9.26 cu yds or about 9-1/4 cu yds.
