Weed Control in the Garden


 By Christopher Ramcharan
 Associate Horticulturist
 C.V.I. Agricultural Experiment Station

 Probably no other farm invention has discouraged more
people from becoming gardeners than the hoe. This implement
is still with us, but the modern gardener with access to an in-
creasing number of herbicides (chemical weed killers) may be
tempted to discard the hoe as obsolete. However, the battle against
weeds is not that easily won. Every method of weed control has
its disadvantages and just as many seedlings have been cut off
by a misguided hoe, many plants also have been killed by im-
proper applications of herbicides.

 A comprehensive approach to the problem of weed control
includes identifying the particular weeds, evaluating the advan-
tages of each method of-control and selecting the right combina-
tion of measures to use. A total weed control program involves
both mechanical and biological control and the proper use of
herbicides only when other methods fail.

 The common mechanical methods -- cultivation and mulch-
ing -- and the biological means of growing healthy plants are widely
discussed in garden articles and books. On the other hand, the use
of herbicides is much more technical and difficult, and much less
discussed in terms the average gardener or farmer can use.

 Gardeners often use one or more mechanical means of weed
control. The most common and readily available is the hoe. A
sharp hoe is an effective means of cutting off weeds but it does
not provide a permanent control. Hoeing is best used where the
young weeds can be uprooted and left to die as their roots dry out.
This is especially effective if done a few days after every rainy
period before the weeds can become fully established. There are
many other tools of cultivation such as versatile tillers, garden
cultivators and even plows. However, cultivation is not always
practical as for example in a thickly covered bed or in the home
lawn.
 Hand pulling of weeds, although time consuming and labor-
ious, is often the safest method. Although very useful in removing
annual weeds, hand weeding, like hoeing, does not give permanent
weed control. New weeds will soon germinate and begin growing.

 A third method of mechanical control is the use of mulches.
The perfect mulch is one that smothers all weeds it covers, kills
germinating weed seeds and has an upper surface that remains dry
most of the time, so preventing germination of weed seeds blown
in from surrounding areas. There is no perfect mulch but there are
some materials that do control weeds quite well.

 A coarse textured mulch is best because larger particles
dry out quickly, so preventing weed germination. Some locally
available coarse materials are wood chips, shredded bark, whole
or crushed mahogany fruit shells, washed sea weed and cut grass.
Mulch materials such as peat moss and sawdust are too fine in
texture. Sawdust, although easily available, does not dry out
easily and has the added disadvantage of depleting soil nitrogen.
If sawdust must be used then added fertilizer should be applied
to restore soil nitrogen.

 Besides being coarse, a mulch should be deep enough to


Mulch keeps down weeds in garden rows and can be made from
wood chips, bark, mahogany shells, sea weed or cut grass.

smother existing weeds and kill germinating ones. Very often
gardeners spread mulches too thin and bare soil is left in patches
resulting in weed growth scattered throughout the garden. A
mulch should be at least two inches deep and up to a maximum
of about four inches. One cubic yard of mulch will cover about
150 square feet to a depth of two inches. Locally, an estimated
20 to 25 tons of cut dried grass is required per acre for effective
weed control.
 Another method of mulching is by use of plastic film, with
or without a covering of organic matter. Plastic films can effec-
tively smother weeds but they must be thick enough -- from four
to six mil gauge -- so that tough weed seedlings will not grow
through. Black plastic tends to build up soil temperature while
clear plastic allows weeds to grow and remain green. Also plastics
do not break down and cannot be incorporated like organic mulches.

 Environmentalists always prefer biological control of pests.
 Usually when the term "biological control" is mentioned we
 immediately think of insects and diseases, but this method can be
 applied to weeds also. The use of geese and ducks, although not
 very practical for the home gardener, is a common method of
 controlling weeds in some countries. Providing optimum growing
 conditions for the plant is an important form of biological control
 that is often overlooked. Proper cultivation of the soil, incorpor-
 ation of soil amendments and the use of fertilizers all aid in getting
 seedlings off to a good start. Finally, keeping the adult plants in
 a healthy condition, free of insects and diseases, helps them to
 compete with and outgrow weeds.

 The farmer uses all three methods of weed control -- mech-
 anical, biological and chemical. He can cultivate his field to remove
 weeds and apply herbicides to kill existing weeds or to prevent