One must realize that to stop
weeds entirely is an ecological impossibility, we may as well
hope to stop the wind. The
best we can hope for is to keep them contained to a minimum.
Most people establish their
new gardens with the subconscious assumption that they will
be static. This could not be further from the truth. Mulch
breaks down, some of the chosen plants will grow while some will
die and weeds will be constantly invading. A garden is as dynamic
as a bush reserve and requires many of the same management
strategies, albeit on a smaller scale.
With respect to weeds, we must arrange conditions in our
garden to make it as difficult as possible for weeds to become
established and prevent the ones that do from reproducing.
However just about everything that the average gardener does runs
counter to this.
Top
To understand why we must first
understand the ecological nature of weed plants. In most cases
they are what are referred to as 'colonizers' and 'secondary
colonizers', i.e. plants that act as pioneers for newly created
substrates that are free from plant growth. These substrates
include a cooled lava field, a site of massive erosion, a
bushfire site or a ploughed field.
Colonizing plants are the
first ones to gain a foot hold in
these new substrates where they are free from competition for light, moisture and
minerals from any other plants. They in fact make it easier, over
a period of time, for secondary colonizers to gain a foot
hold. Over a very long period of time the colonizers are
themselves replaced by larger trees and shrubs.
Top
Among common practices, used by the average
gardener, that greatly enhance the establishment and spread of
weeds are:
- Cultivating the soil - this
removes all weed plants and temporarily makes the garden bed
look neat. But it also removes all competition for tiny weed
seedlings that will spring up from seeds lying dormant in the
soil.
- Spacing the plants to far apart
- this allows weeds to receive ample sunlight and space thus
promoting their growth.
- Frequent surface watering - as
well as being good for your garden plants it is also great for
weeds. It is much better to keep watering to a minimum and
plants that don't require much watering can obviously help.
- Surface application of
fertilizers - clearly this will induce a growth spurt in the
weeds as well as your plants. Slow release fertilizer are
better as the minerals will not be immediately available to
the weeds.
- Not laying mulch thick enough -
to be effective mulch really needs to be several centimetres
thick when it is first laid to allow for compaction. Otherwise
it provides an inadequate barrier.
- Not using abundant ground cover
in their garden beds - ground cover plants exert significant
competition for space, water and minerals on young weed
seedlings and will prevent many of them surviving.
- Weeding at the wrong time of
year - most people wait till late spring or summer to weed
their gardens by which time it is far to late.
Top
This last practice is the most
important one to change. By allowing the weeds to shed their seed
into the soil you are maintaining a seed bank that can contain
years worth of seeds from which those hated weeds will be
continually replenished every spring.
By far the best time to weed your
garden beds is early spring while the weeds are flowering and
before they have shed seed. Any new ones that pop up later in
spring and in summer, again get rid of them before they finish
flowering.
If all your other techniques must
work in harmony with consistent weeding then that weed seed bank
can be greatly diminished over a period of years. In so doing you
will get to the point where weeding your garden is no where near
the daunting task that it starts out as.
The other thing to watch out for
is weed growth in neighbouring properties. If it is extensive
then it will be dispersing seed into you property via wind. The
best way to deal with it is to plant a dense screen of shrubs
that will largely block entry of wind borne seeds.
Top
- Keep any form of soil
disturbance to an absolute minimum, in order to avoid creating
those new substrates that weeds thrive in.
- Crowd your garden beds with
plants in order to increase competition with weeds for space,
light, minerals and water.
- Use plants that don't require
much watering and keep watering to a minimum. This will reduce
the germination of weed seeds in the soil.
- Apply fertilizers in the base of
the holes when you first plant your plants and avoid applying
them once the plants are established. This will keep it out of
reach of weed seedlings.
- Lay mulch to a depth of several
centimetres and use shredded green waste or composted green
waste. In a relatively short period of time this material
forms a dense crust in which the seedlings of many weeds find
it difficult to establish in.
- Plant your garden beds densely
with ground cover. Again this will increase competition with
weeds.
- Carry out you weeding
consistently in early spring and keep on top of new weeds
through the spring/ summer period.
Top
Weed control, particularly on a large
scale, is an intensive and expensive exercise and often feels
like one is trying to hold back the tide. On new or neglected
sites relying on non-chemical means is largely an exercise in
futility. And so we are stuck with
the necessary evil of using herbicides until a better and cost
effective means of weed control come along. However
there are a number of upsides to using herbicides: Biodegradable
Although current herbicides should be
treated with respect, in terms of environment and OH & S, we
have come along way since the days of DDT. Apart from a few long
lasting residual herbicides used for specific purposes, most of
them break down in soil over a period of weeks or months,
depending on moisture levels and microbial activity.
Integrated Weed Control
Herbicides are useful for gaining the upper
hand over weeds, however they should be used in combination with
other methods such as hand weeding and establishment of competing
ground covers and shrubs etc.
Establishment of indigenous ground covers
and shrubs are by far the most cost effective means of
suppressing weed growth and are also great for the environment.
If sufficient time and effort and vigilance
is put into weed management of a site then you should be able to
get to the stage where herbicide usage is a minimal or negligible
component of management strategy. This state of affairs is
normally quite easy to attain with suburban gardens.
Selective Herbicides
Roundup is the 'shot gun' of the herbicide
suite effecting most plants over which it is sprayed. However it
is important to note that it is most effective on monocotyledons
such as grasses but often less effective on dicotyledons such as
Malva sp or the Mallows. In the case of Malva it will sicken the
plant but does not normally kill it outright. More
useful are the selective herbicides which are more like 'sniper
rifles'. Here are a few: Fusilade
This only kills grasses and so you can
spray it over your shrubs, herbaceous plants, lilies and rushes
etc to rid your garden beds of Kikuyu and other weedy grasses. MCPA
This only kills herbaceous dicotyledons,
may or may not kill woody dicotyledons but does not effect
grasses. Hence it can be sprayed over your lawn to selectively
eliminate the broadleaf weeds such as flat weeds and medics etc.
It is present in the 'Weed & Feed'
preparations for lawns. However it
does kill or effect rushes and sedges, closely related to
grasses, so be careful. Garlon
This kills both herbaceous and woody
dicotyledons but does not effect grasses, sedges or rushes. It
can therefore be used to eliminate broadleaf weeds from
lawns or weedy shrubs from mass plantings of native grasses,
sedges and rushes. Exceptions
It is always a good idea to test any
particular herbicide on your garden plants because exceptions to
the rule do crop up from time to time. This can be accomplished
by painting a bit of the mixture on a few leaves and watching for
any wilting or discolouration. For
example Garlon, which does not normally effect grasses, does
knock the indigenous grass Microlaena stipoides.
Top
|
