Weed control in the home garden

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 desirable plants.

Weeds are a part of nature. They are the natural vegetation and have therefore adapted to thrive in the  position they are in. Many of our domesticated plants whether they be vegetables, fruits, or ornamentals are sometimes overtaken by weeds. A weed is defined as a plant growing out of place. 

From a 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.

 Methods of controlling weeds.

• Cultivation or hand weeding.
• Mulching- covering the surface with a mulch of compost, shredded green waste, straw, or weed mat plus stones.
• Planting dense strong growing ground cover plants that suppress weeds. 
• Use of an appropriate weedkiller—used correctly

From the beginning

Before any garden or lawn is planted, check if there are any existing aggressive, difficult to control perennial weeds such as couch grasses, convolvulus, docks, tradescantia (wandering jew), periwinkle, yarrow, agapanthus etc. If these weeds are present they should be eliminated first. Occasionally physical removal is possible, but for weeds with aggressive extensive underground roots the most effective method is to use a herbicide. See below under specific weeds for more detail 

 Vegetable garden

Regular cultivation between rows and hand weeding are still the safest and most effective control measures for vegetables. Mulching with compost, straw or similar is also very effective at suppressing weed germination. A negative can be that birds are attracted, scratching out newly planted seedlings in their efforts looking for worms. So, bird protection may also be required.

It is so important to not let weeds seed as this will make the weed problem worse next year - 'One year of seeds equals 7 years of weeds’ is very true. 

Flower garden

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 plus 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, while allowing rain to enter and the soil to breathe. A more decorative mulch such as granulated bark or stone can be placed on top of the weed mat. Mulching has an additional benefit of keeping the soil moist, resulting in healthier plants. 

Lawns.

Emergence of annual weeds in new lawns is common. The first few mowings of a new lawn eliminate or suppress most weeds over the first few months. Once the new grass thickens up, weeds diminish. Feeding lawns with lawn fertilizer three times a year will maintain a strong sward. Setting the mower at a medium to high level will also keep weeds supressed.
There are a few common weeds which tolerate  regular mowing and may require application of a herbicide. Do not apply a weed-spray to new lawns until they are at least 6 months old, preferably 12 months.

Start withYates Turfix, Grosafe Lawnguard, or Kiwicare LawnPro Turf Clean. These products will give a good result for most common broadleaf weeds when correctly applied at the correct rate per sq.m.     

For more persistent weeds;          

• Onehunga Weed (Prickleweed) is controlled with Yates or Grosafe Prickleweed killer.
• Hydrocotyle and creeping oxalis are controlled with Yates or Grosafe Hydrocotyle Killer

Unfortunately grass weeds such as paspalum, cooch/twitch, kikuyu (in certain situations) etc are not controlled by lawn weed spray. Any spray that will deal with them will also kill your grass. If the problem is widespread, you will get the best results from spraying off your lawn, ensuring the problem has gone before resowing a new lawn. If the problem is new and only in isolated spots, deal with it quickly and spot spray to wipe it out.

For more difficult weeds and a full list of herbicides refer to Pro Advice section. (Coming soon)

Specific Difficult Weeds

Difficult perennial, bulbous, or woody weeds can be controlled with one of the following -

• Amitrole—Periwinkle, Wandering Jew, Wild Onion, Bamboo, Oxalis
• Woody WeedKiller— For most woody weeds.
• Glyphosate—Controls most difficult weeds when Ecospread penetrant is used with it. 
• Zero Tough - Arum Lily, Blackberry, Agapanthus, Gorse

More powerful herbicides are available to home gardeners, but great care is required with their use in order to protect desirable plants and the soil. This detail is covered in the Pro Advice section (coming soon)  

 Driveways and waste areas

The most cost effective weedkiller here is a glyphosate product such asGrosafe Knockdown, Yates Zero, Kiwicare Weed Weapon Extra Strength, or Roundup.

These products kill a wide range of weeds and grasses without harming the soil or people .  

Contrary to popular belief glyphosate is very low risk to people and the environment. See full details of official science and legal status under Pro Advice (coming soon)

Organic alternatives for general weed control

• Round up Natural or  Goulters WeedX – containing vinegar. Vinegar is a scheduled poison so cannot be sold to gardeners in concentrate form. Therefore, these two products are available in a ready to use form only, which is very expensive.
• Slasher – a new product based on a plant acid.
• Yates Natures Way Organic Weed Gun; Kiwicare Weed Weapon Natural Power  

All these organic products kill weeds by contact action alone. They are effective and fast acting against small annual weeds. They temporarily burn the tops of perennial weeds but do not kill the roots, which rapidly regrow. They are more expensive than glyphosate. These contact weedkillers are useful for spot spraying close to desirable plants as any drift causes minimal damage.

 For more information on weed control, useful ground cover plants, a full weed list and more information on each herbicide, join Advice Pro (coming soon)