A 5 minute read by Peter Worsp
Perhaps the main reason we control weeds is because they give the house and garden an untidy, uncared for appearance.
However, in the garden they compete with plants for light, moisture and nutrients. They can totally smother and kill small less vigorous plants.
This article outlines control measures for different situations.
Weeds are a part of nature. They are the natural vegetation and have therefore adapted to thrive in the particular position.
In the garden we will aid weed control by selecting plants which thrive and compete with weeds, rather than plants which are weak and unsuited to the area.
From the home gardeners point of view weeds fall into two broad categories.
- Annual weeds, which are mainly a problem in cultivated vegetable and flower gardens
- Persistent perennial weeds which tend to compete strongly everywhere
In addressing weed control, it is important to consider in what situation is the weed growing. Hence this article discusses each situation in the home garden. For very specific weeds, have a look at our "Which Weedkiller to Use in Home Gardens" chart.
Driveways and Waste Areas
The best weedkiller in this situation is a glyphosate product such as Weed Weapon or Knockdown. These products kill the widest range of weeds and grasses. Mallows and clovers are the only common weeds somewhat resistant.
- Glyphosate products rapidly bio-degrade on contact with the soil
- They are of very low hazard to people and the environment
- Regular cultivation between rows and hand weeding are still the safest and most effective control measures for vegetables
- Mulching with straw or similar is also very effective at suppressing weed germination
- It is also important to not let weeds seed as this will make the weed problem worse next year
For annual bedding plant areas the same comments apply as above for vegetables.
Shrub and Perennial Garden
Here the best result is achieved by using a combination of strong growing ground cover plants or shrubs and mulching each year with straw or a garden mulch.
For a more permanent mulch and less work, weed mat can be used. This is a woven plastic sheet which when laid on the soil surface will stop weeds germinating, but allows rain to enter and the soil to breathe.
- A decorative mulch such as granulated bark can be placed on top of the weed mat
- Mulching has an additional benefit of keeping moisture in
- Weed Weapon and Knockdown can be used to spot spray difficult weeds that persist, but care must be taken to ensure no spray contacts leaves of desirable plants
- A well drained, well fed lawn, that is mown high rather than short, will suppress weeds quite effectively, minimising the need to spray
- The soil for lawns should be moderately acid. Therefore do not apply lime. Gypsum can be used as an alternative to lime
- Weeds in lawns can be suppressed by topdressing 3 or 4 times a year with Tui Lawn Food. In addition it is recommended that lawns are mown at a high level rather than short. This allows the grass to grow thicker and suppress weeds
- Weeds in new lawns largely disappear after 5 or 6 mowings
- Once the lawn has been established for a year, most weeds and clover can be controlled with LawnPro Turfclean, a mix of three ingredients to give wider control.
- Turfclean is best applied in early spring (Mid – late Sept), especially for control of Onehunga - Prickle weed
- If Hydrocotyle and Prickle weed is a serious problem, use LawnPro Hydrocotyle & Prickle Weed Killer
- If moss is a problem, consider whether the lawn is too shady, poorly drained, receives insufficient fertiliser, or is mown too short. It is important to correct these deficiencies first, or moss will continue to be a problem
- LawnPro Mosskiller can be used to control moss