As previously discussed under site preparation, weed control is usually the single most important factor in the success or failure of tree plantings. It is just as critical after planting as before and should be continued for at least one full growing season after planting and preferably for 2 years. A weed-free area of 1m diameter should be maintained around each plant for this period.
Weeds should be controlled when they are actively growing, before they set seed and before they begin to compete with your newly established plants. Different weeds will germinate at different times of the year so you will need to monitor your site regularly. Look at your site each month after planting and schedule weed control when you see actively growing weeds. It is much easier to control weeds before they get too big and before they set seed. If you have an annual program of revegetation planned, it pays to keep records of which weeds occur and when they emerge, as well as effective techniques for their control.
This website will help you to identify weeds. It contains an interactive tool which enables you to select your area and look through a list of weed species known to occur in your region, with pictures and information about them.
The Weeds CRC produced a range of weed management guidelines that you may find helpful to tackle specific problem weed species.
Another useful publication is 'Stop Bushland Weeds' by Meg Robertson. This publication also contains a table which shows the most effective times of year to control particular weeds.
When using chemical weed control, only chemicals known to not harm your plant species should be used where the chemical is sprayed over the whole site. Otherwise the chemical can be applied in such a way as to avoid contact with your new plants. Shielded sprayers, wick-wipers or backpack sprayers can be used. Specific chemicals can be used to control weeds without affecting the newly established plants. There are several grass-specific herbicides available which will not affect shrubs and trees. Other chemicals can be used as an overspray with no or little effect on native species, however you should get specific advice from an experienced operator before doing this. You should discuss the possibilities with an agricultural chemical supplier or agronomist to find a suitable chemical and application method for your species and region. The Pest Genie website can also help you find the most appropriate herbicide for your situation.
Your local NRM Regional body should also be able to help with weed control methods, timing and safety measures. Click here to find your local NRM regional body. Nationally accredited Farm Chemical User training should be undertaken if you are planning to carry out this work yourself.
Non-chemical methods such as hand weeding, mowing or mulching can also be used. For example, or weedy grass species, mowing when the exotic grasses flower, but before the native grasses do, gives the native grasses an advantage. If repeated over successive years, this method has been shown to increase the cover of native grasses and reduce the area of exotic grasses.
The WA Department of Agriculture has an excellent field note on weed control for revegetation, including post-planting weed control, with some specific herbicide recommendations.
A good site to get some information on chemicals for use in weed control is from the Adelaide and Mount Lofty Ranges NRM Board, which has produced 10 fact sheets on responsible chemical use. The Adelaide and Mount Lofty NRM Board, South Australia, also has a useful website about techniques for controlling weeds in bushland and revegetation sites.