Physical Control of Weeds

Physical Control

Physical control

The removal of weeds by hoeing, mowing, mulching, tilling, burning, grazing or by hand is a good method for selective removal of weeds without disturbing the surrounding desirable vegetation. However, it is very labour intensive and is often only used in small areas, such as gardens or in larger areas during bush regeneration. To be successful minimise disturbance, removing isolated weeds in areas of good bush and agricultural land first, rather than tackling a dense infestation. Hand-pull weeds from moist soil or after rain, then fill in holes with soil and pack down firmly. Cut and paint stems rather than pulling out large plants. Don’t pull or rip down climbers from trees as damage can occur to native or non-invasive species.

Tilling turns over the soil and buries weeds beneath the soil, providing a barrier to the sun, thus killing the weeds. Using agricultural machinery tilling can be easily undertaken over a wide area and is used for making soil ready for planting new crops. However, it can also lead to damage within the soil’s structure and exposes the soil to erosion and further invasion by weeds.

Thermal weeding using heat in various forms (radiant, flame, steam, hot water) to kill plant tissue is another option. Burning either on a large scale or with a hand burner or propane torch can be effective in the right conditions as it removes the above-soil body of the weeds killing most of the plants. Choose a time after rain or at least when any nearby plants or mulch are soggy and wet. Have a water hose handy or a watering can to dowse any sparks. If carried out before seed is set it can prevent the further spread of weeds. Burning can be undertaken over a wide area with minimal human input, however, this sort of burning also exposes the soil surface to erosion. If burning is used as a control method, caution should be exercised to minimise the risk of harm to the environment and to those undertaking the activity. Obviously windy days and high temperatures should be avoided and the availability of a water source is important as even in the home garden fire can get away quickly.
Boiling water is also effective on weeds if you only have a small area to control. This should also kill some surface un-sprouted seeds too. Be careful of your hands and feet, and keep children and pets away. Go slowly and concentrate when carrying the hot container.

A steam machine can be used to control weeds for a larger area. Precious plants should be covered up to protect them.

Soil solarisation kills weeds and can actually sterilize the soil and kill all life if hot enough. You need plenty of sun for this method to work. Transparent plastic lets the light in so will encourage the weeds to grow initially, but then they will get severely burnt by the direct sunlight, as well as allowing heat to build up under the clear plastic. Black plastic absorbs the heat, blocks the light and cooks the weeds and soil underneath.

Applying thick mulch all year round to inhibits weed growth and germination of weed seeds by blocking sunlight and light rainfall from reaching the soil surface. Using old carpet for large areas to smother weeds results in the ground being perfect the following year to plant into as the worms have done all the work turning weeds into soil. Layers of newspaper covered with a heavy mulch are also effective but again if you live in a bushfire prone area you will need to use a different method.

In the vegetable garden use companion planting to fill spare spaces with flowers and herbs with foliage that smothers weeds. This also has the advantage of attracting bees.