Gardens come in many shapes and sizes but one
thing they have in common are weeds. For many gardeners, trying
to control weeds is a never-ending struggle.
One reason for controlling weeds is that they
spoil the appearance of gardens. Another is that if they are
not controlled early, they increase and spread, and are more
difficult to control later. Probably the most important reason,
yet one that is often overlooked, is that they reduce the
growth of neighboring plants, mainly through competition for
water and nutrients. Even trees and shrubs, especially during
their early years, are sensitive to competition. Because all
growing plants remove water and nutrients from the soil, even
lawn grasses and ground-cover plants can be considered "weeds"
if they are too close to trees and shrubs.
Hand-hoeing is still the best method for the
home gardener. It is inexpensive, quite selective, accurate,
effective, and for some people, even enjoyable. A great deal
of emotional satisfaction can come from leaning on a hoe handle
while viewing a clean, freshly?hoed row where weeds grew only
minutes before. When hoeing, a fair amount of hand pulling
is usually necessary if weeds are growing close to the base
of the desirable plants. A fair amount of damage may occur
to vegetables if weeds are allowed to get big before being
pulled. Other alternatives are mulching and using herbicides.
Mulching controls weeds by keeping light away
from seedlings and providing a mechanical barrier to emergence.
It works best against weeds that come up from seed each year.
Weeds that do come through the mulch are easily spotted for
removal and are easily pulled from the moist soil.
Good mulching materials include compost, straw,
leaves, hay, sawdust, wood shavings, bark, paper and plastic
sheeting. The most popular synthetic material presently in
use is 1 and 1-1/2 mil. black polyethylene film. Clear plastic
may be unsatisfactory since it allows light to enter, encouraging
weed growth under the plastic. Black plastic will heat soils
faster. All plastic mulches should be removed when hot summer
days begin since they can actually overheat soils. A good
source of plastic mulch is garbage bags that have been split
on one side so that they cover the planting bed. Plants are
planted in holes made in the plastic covered beds. Organic
mulches form a barrier which will not allow soil temperatures
to change rapidly. This is a benefit in the hot summer since
the soil remains cooler but can cause plant injury from frosts
in the early spring because there is no release of soil heat.
Herbicides provide new opportunities in weed
control. They can prevent weeds from emerging, kill weeds
growing near to garden plants and control deep-rooted perennials
without disturbing the soil around desirable plants.
One of the available herbicides is glyphosate,
sold as Roundup, Kleen-up, Doomsday and Weed?and?Grass Killer.
check the label for the term "glyphosate." There
are some grasses and weeds, such as bermuda grass and Johnson
grass, which resist pulling and hoeing. They actually grow
better the more you cut, pull and hoe! When used as directed,
glyphosate-containing herbicides effectively control many
weeds that other herbicides cannot control, and have no adverse
effects on cropping systems or the environment. The "active"
ingredient in these herbicides is the isopropylamine (IPA)
salt of glyphosate (N?(phosphonomethyl) glycine). The nutrient
transport system of the plant is utilized for translocation
from the plant foliage to the underground root or rhizome
system. Symptoms of activity develop slowly, and weed damage
may not be obvious for 4 to 6 days for annual plant species
and up to 10 days or longer for perennials. Visible effects
are a gradual wilting and yellowing, which advances to complete
browning and deterioration of plant tissue.
Glyphosate-containing herbicides are most effective
when applied to the foliage of actively growing annual and
perennial weeds or brush. Control of perennial weed species
is most effective when applications are made at, or beyond,
the early head or early bud stage of growth.
Mowing or tillage operations should not be
done prior to, or immediately after application, since sufficient
time (3 to 7 days) must be allowed for translocation. If weed
foliage is removed, it must be allowed to regenerate sufficient
size to permit uptake and movement through the plant.
Upon contact with the soil, glyphosate is inactivated.
The herbicide is tightly bound by the soil particles, preventing
glyphosate uptake from soil by plant roots. This binding also
prevents leaching and lateral movement through the soil. When
applied to the soil at test rates 30 times the normal use
rate, glyphosate-containing herbicides did not affect the
growth of crops planted immediately after treatment.
Seeding of crops should be delayed until the
treated vegetation dies. The success observed with this delay
may be related to: (1) improved soil moisture conditions,
(2) insects and soil biota, (e.g., slugs, snails) that feed
on emerging seedlings, leaving the dead vegetation, and (3)
dissipation of toxic substances produced by some types of
dying vegetation. Since glyphosate has no residual soil activity,
it will not control weeds that emerge after application.
For maximum weed control with glyphosate-containing
herbicides, good application conditions are important. Application
is not recommended when winds favor physical drift of spray
solution, or when rain is expected within 6 hours. The weed
foliage should be dry and free of visible dust cover that
could interfere with proper absorption of the herbicide. The
formulation is non-volatile and will not damage any plant
not contacted during application. If a non-target plant is
accidentally sprayed, immediately wash or rinse the foliage
with water to avoid uptake and later damage or death.
Proper translocation occurs only in actively
growing weeds. Reduced control may result when treated weeds
are not actively growing due to stress caused by drought,
insect damage or disease. Although extremely cool or cloudy
weather may delay visual symptoms of control, weed control
is not reduced.
There is a "natural" herbicide that
is recommended by some people. Malcolm Beck, founder of Gardenville
Products in San Antonio writes: "Corn gluten meal is
a high protein that makes it about 10 percent nitrogen. Apply
it as you would a fertilizer, about 20 pounds per square feet,
to the top of the soil. You may scratch it in lightly, then
water enough to sprout seeds and hope it doesn't rain. It
needs to stay dry. The seeds sprout, but for some reason the
roots do not develop. If your timing is too early for the
weed seeds and there was continuous moisture, such as rainy
spell, the microbes eat the meal before it can do it's thing
to the weed roots, and then you got the healthiest weeds you
ever saw. The trick is, knowing when the native weed seeds
are about to sprout. Once a root is established, the meal
has no effect. This is an excellent fertilizer for perennials
such as strawberries, blackberries, lawns and such. This is
an organic weed and feed. It is a win, win or just a win situation.
Either way you win."
Most annual weeds can be controlled by cultivation!
Annual broadleaf weeds are easily removed while they are in
the seedling stage. Cultivations should be made to control
each flush of weeds that emerges, usually within a few days
after a rain. At this time, weed seedlings are easily uprooted
even with hand?pushed garden plows, hoes and other hand tools.
If weeds are allowed to get very large before
control measures are taken, their root systems will develop
to such an extent that removal with a garden plow or hoe will
be difficult, if not impossible. The old saying, "nip
it in the bud," certainly applies to weed control in
The first few weeks after vegetables are planted
is the most important time to control weeds. After the vegetables
get well established and start shading the ground, they become
competitive and do a good job of preventing new weeds from
By following good cultural practices and using
mulches along with the timely cultivations and hand hoeing,
most annual weeds can be controlled in home gardens without
excessive "back?breaking labor." In fact, if done
in time the exercise required to control weeds in home gardens
would be beneficial to most of us. If nothing else, it should
stimulate our appetites and make us appreciate those delicious
vegetables being produced.
No one method of weed control is best for all
situations or problems. Personal preference, size of garden
and the time available are just some of the factors to be