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Mulch is used as
a cover to protect and nourish soil. Organic materials are
usually used as mulch, although inorganic materials such as pebbles can
be used. Bare soil rarely
occurs in nature, and in most cases it is best avoided in the garden.
The depth of mulch can vary, from a light sprinkle between seedlings,
to a no-dig
garden with 15cm or more of deep mulch which is used as a growing
Benefits of mulch
water evaporation arising from protection of soil from the drying
effects of wind and sun.
of organic matter and nutrients, improving fertility, structure and
biological activity within the soil.
soil surface condition, eliminating problems of crusting and assisting
with non-wetting soil.
dirt splash, a problem that can create diseases in plants.
weeds by smothering and limiting germination. Invasive weeds can be
easier to manage.
beneficial predators such as spiders and centipedes.
erosion by slowing the movement of surface water.
extremes of soil temperature.
Problems associated with mulch
Some mulch materials
- In dry weather, water can be prevented from reaching soil.
pests such as slugs, snails and earwigs.
warming is slower in Spring.
- Fine thick
mulch can block air from entering the soil.
weeds, with a mass of fibrous roots, can be difficult to remove without
losing lots of mulch.
gardeners see organic matter as a resource to be gathered rather than
as a waste product. There are many different kinds of materials that
can be collected for using as mulch. Look aroung to find what is
Straw and hay
Any straw or hay is suitable for vegetable and flower gardens. Avoid
material with weed
seeds. Shake the hay before adding it to the garden if you suspect it
contains seeds. Lucerne hay is the best mulch material as it
contains a good range of essential elements. Pea straw has reasonable
nitrogen content but is very light and breaks down quickly.
These woody materials form a long term
attractive cover, especially suitable for landscaping and ornamental
gardens. Sawdust is good on pathways.
Large leaves should be shredded or mixed with other materials
before being used as mulch or they will form a matted waterproof layer.
Some leaves, such as eucalypt, walnut and pine (acidic), have an
adverse affect on soil life. Leaf mould, made by allowing a pile of
leaves to completely decompose, is a good mulch and a good soil
An excellent coarse mixture of wood chip and leaf.
Home shredders can turn prunings into mulch. Large quantities may be
purchased from garden supply depots. Avoid eucalypt, olive (which may
contain seeds) or pine based shredded mulch.
Use under other materials to smother weeds. Do not leave
paper uncovered or it will get blown about and create a mess. Glossy
coloured paper is toxic and must not be used.
Long lasting cover which breaks down very slowly. Collect after rain to
avoid salt or water it down before applying.
Check with Council for permission before collecting. The last time I
asked it was allowed to gather seagrass by hand, provided vehicles were
not brought onto the beach.
Do not apply lawn clippings too thickly or they will
go slimy. They do not last long and break down quickly. They may
contain couch or kikuyu pieces, which can regrow. The properties of a
lawn clipping mulch depend upon the type of lawn. Clover provides a
higher nitrogen content, whereas kikuyu is fibrous, with a higher
proportion of carbon. Lawn clippings are very fine. They are best used
on top of other,
more open, mulch materials.
Provided they are harvested before seed set, weeds make an
excellent mulch. Invasive weeds which might regrow should be dried out
before being used as mulch.
Old Garden Plants
When you take out those old vegetable plants, you can chop them with a
spade a couple of times then leave them in the garden as mulch. Keep in
mind the need to avoid spreading plant diseases - tomatoes for example
should be composted..
Poultry litter - Any of the materials listed above may be
left in a chook yard
for a while before using as mulch. Chooks will clean out weed seeds and
add manure to the mulch.
Manures - Do not apply raw manures directly to the soil unless they are
mixed with and covered by a large bulk of other mulch materials.
Failure to follow this rule will result in an unhealthy offensive
The use of plastic as mulch is not recommended. Plastic will not break
down and will become a nuisance later. Although plastic, used with
other materials, provides an effective weed smother, many invasive and
persistent weeds grow through the plastic, which obstructs the gardener
when trying to clear these weeds.
Small stones, gravel or pebbles are an attractive mulch. They provide
many of the
advantages of an organic mulch, without the benefits of improving soil
fertility. Water penetrates quickly through It can be tricky
using garden tools to weed through gravel. When planting trees for
revegetation work, you can put around each tree a mulch of stones or