While one person's garden weeds are another's decoration, it's helpful to be able to identify the problem plants in your garden - those that are depriving other plants of light, space and nutrients. This handy guide teaches you how to identify and control weeds for a cleaner, healthier garden.
- Herbicides - as required
Step 1. Know the enemy
Before you can successfully control or eradicate weeds, it is important to understand their characteristics and growth habits. Generally, all weeds have some of these basic traits:
- vigorous and persistent growth, allowing them to establish themselves quickly and often grow faster than plants already there;
- difficulty in eradication;
- propagate easily from roots left lying on the ground;
- a short life cycle of some weeds means seed is produced quickly;
- produce large quantities of seed;
- spread seed quickly through special dispersal methods such as burrs;
- seeds can remain dormant in the soil for many years.
Like all plants, weeds fall into two main groups. You need to know this if you are planning to use a chemical (herbicide) to control a particular type of weed.
Plants producing one seed leaf when they germinate. The leaf is long and narrow, and has parallel veins, eg. grass.
Plants producing two leaves on germinating. Leaves are broad and have a network of veins, eg. clover.
You should also know whether weeds grow annually, biennially or perennially – this can determine your method of controlling them, either by chemical or mechanical means.
Annuals complete their cycle in one year or less and may have several generations in that year. Aim to destroy them before they produce seed. Some examples are Cape Weed, Winter Grass, Stinging Nettle, Chickweed, Bindii and Petty Surge.
Biennials have two year cycles, flowering and producing seed in the second year. They should be destroyed in their first season. Examples include Fennel, Patterson’s Curse, and Evening, Blackberries, and Carpet Grass are prime examples.
Step 2. Weed control
Most weeds in the home garden can be effectively controlled with good garden practices such as:
- removing weeds as soon as they appear;
- mulching where possible to suppress weed growth;
- ensuring soil introduced is free of invasive weeds;
- removing annual weeds before they seed;
- removing perennial weeds before they seed and ensuring you get their roots as well.
Probably still the best method in the home garden or for small areas.
Using a garden fork, cultivator or Dutch hoe to remove weeds is the most practical and sensible method in many cases. The secret is to spend just a few minutes a day when the weeds are small and easy to remove rather than putting it off until the problem gets out of hand. Then it becomes a back-breaking task – and an unnecessary one – spoiling your pleasure of gardening.
Regular mowing of lawns prevent taller weeds from flowering and seeding.
Smothers weed seedling before they become a problem and has the added benefits of keeping the soil moist and cool in summer.
Step 3. Using herbicides
First, read the instructions on the container and follow them carefully. Herbicides are poisonous so familiarise yourself with first aid directions, too. Mix only according to the directions and apply with a sprayer or watering can. Avoid spraying on windy days where spray mist could drift onto cultivated plants. It could also blow onto you, so wear appropriate protective clothing. After use, thoroughly wash out the sprayer or watering can. Wash yourself thoroughly, too, particularly hands, arms and face. Finally store chemicals in a safe place, out of reach of children, and dispose of empty herbicide containers according to label instructions.
These must be used with great care. Choose a day when there is little or no wind to cause drift onto your cultivated plants and killing them, too. In area where long term control is required, such as along fences, pathways, driveways and tennis courts, use a once-a-year-path weeder like those produced by Yates and Hortico. They kill most weeds and prevent weed seeds from germinating. But as the name implies, they last in the soil for up to 12 months. So be sure not to use where there’s a chance of the herbicide running on to lawn or garden beds. In areas where weed killing is required but the ground is to be cultivated and planted up shortly afterwards, Mitre 10 Glyphosate is recommended. This herbicides has no residual effect on the soil and the area treated can be used within 2–3-weeks.
These kill only the weeds they are made to eradicate, and there’s a range of them for lawns depending on the problem. For example of only broad leaf weeds (the Dicots as mentioned earlier) while leaving grass (Monocots) to flourish. As with weedkillers, be careful of spray drift on to cultivated plants. And do not use grass clippings from the treated area for mulch or as feed for livestock. Bindii is a common problem in lawns in New South Wales, Queensland, Victoria, Tasmania and South Australia and spraying with Yates Bindii & Clover Killer when actively growing can control it.
Other selective herbicides are available to control Paspalum, Crab grass, Mullumbimby, Couch, Winter grass, and Carpet grass. As defined earlier, a weed is a plant growing out of place. And in lawns, this can be any grass different to the chosen lawn grass. For example, Carpet grass infestation in a lawn of Queensland Blue Couch – this is best controlled with spot spraying. Amgrow's Paspalum Killer will control Paspalum, Nut Grass, Summer Grass and Mullumbimby Couch in domestic lawns.
Of course, the best way to prevent weeds invading your lawn is to have a regular program of feeding, watering and mowing