Controlling weeds is vital to maintaining a productive vegetable garden. The two broad classes of weeds are grasses and broadleaf weeds. Within each class are perennial weeds, biennial weeds, and annual weeds.

Biennial and annual weeds can be controlled readily by conventional means. Perennial weeds usually have strong, aggressive root systems that serve as a storage mechanism from which the plants re-grow. Examples of perennial weeds are Couchgrass, Dock, and Convulvulus. Perennial weeds frequently require herbicides for control, prior to or after the garden season.

Several good ways to control weeds in vegetable gardens are cultivating, mulching, and using chemical herbicides.

Cultivating the soil after weeds have sprouted in the spring will reduce weeds before planting. Frequent cultivation and hoeing between the rows and around each plant are necessary, especially during the early part of the season. Cultivation during the summer must be very shallow to prevent damage to vegetable roots. Small weeds most often are pulled by hand, particularly in amongst seedlings. Cultivating with a rotary tiller or hoe and pulling weeds are intensive-intensive but effective. Doing this in the morning on a sunny day will cause weeds to wilt and prevent re-rooting.


Straw, old hay, grass clippings, black plastic, and other good mulching materials will not only help control weeds, but will conserve moisture and may add organic matter to the soil. It is best not to apply organic mulches until the soil has warmed, usually about mid-June.

Black plastic mulch can be laid in April. The soil should be moist not dried out when plastic is laid. Transplants can be put into holes cut in the plastic at desired spacings after the plastic has been in place for about one week. Apply fertilisers and work them into the ground before putting plastic down.

In particular, staked tomatoes, peppers, and most transplanted vegetables benefit from a good mulch. However, all vegetables can be mulched to control weeds. It takes 3 to 4 inches of straw for good weed control.

Chemical Weed Control

Chemical weed control in a vegetable garden can save time and work if done properly. Careless application can stunt or kill vegetables, resulting in poor or non-existent control. Herbicides are often very specific in their safety to particular crops. A typical vegetable garden with a variety of different crops is susceptible to injury if a herbicide is applied to an area where a non-resistant crop is planted.

Don't use chemical weed control in your garden unless you are willing to measure accurately and apply materials correctly.

Herbicides are classified into three general categories:

  1. Pre-plant incorporated - Herbicide is applied to the soil and worked into the soil 2-4 inches deep.
    This is done before planting.
  2. Pre-emergence - Applied to the soil immediately after planting the seeds or just prior to transplanting plants.
  3. Post-emergence - Applied over the top of the growing crops to kill weeds that are growing.

The following materials are recommended for home vegetable gardens since they are available in small quantities and are relatively safe to use. Many other available chemical weed-control materials are not included in this list. These herbicides will control most weeds and grasses, but a few weeds are resistant, so hand weeding is generally required.

Various Weedkillers and their uses

Sodium Chlorate

This is weedkiller and is only for use where nothing is to be grown at all. It will kill all top growth and prevent new growth for between 6 - 12 months. Usually in crystal form and mixed with water to be applied with a watering can. (Do not use the watering can for watering your plants afterwards)


This product is also a total weedkiller for use on pathways and areas that do not need to be planted. It also contains a chemical to stop any new seeds emerging. Usually effective for about 6 months. Easy to mix, 1 packet is mixed with one gallon of water.


Weedol will only kill the top growth of plants. Once it has contact with the soil it becomes inactive. As it is only effective on the green leaves of plants, it is good for ground clearance of annual weeds prior to planting. It is quite convenient to mix as 1 packet is mixed with one gallon of water.

Roundup / Tumbleweed

These weedkillers are Systemic. This means that once in contact with the plant it is absorbed into the plants own system and therefore it kills all of the plant including the roots. This sort of weedkiller is used for getting rid of perennial weeds that can re-shoot from the roots. Once in contact with the soil it becomes ineffective so the area can be replanted after a few weeks. Sold in liquid form it is usually quite easy to mix. Can work out expensive if doing a large area.

Brushwood killer / Tough weedkiller

This is used for clearing areas that contain tough weeds such as nettles docks and brambles and may need a re-application depending on the type of plants to be killed off. Usually in liquid form in easy measure bottles.

Methods of Application

These herbicides may be applied with a sprayer or watering can. Be sure to keep them stirred or agitated.

Determine how much area in square feet you can cover with a gallon of water applied with a sprayer or a watering can. Use plain water to try this first. Then apply the herbicide. It is better to make two applications, walking in a different direction each time. Do not backtrack or double the application. Use a convenient amount of water and be sure to apply the correct amount of chemical for the area.

CAUTION: ALWAYS read the label. Apply materials only on crops listed. Follow all directions and observe precautions. Avoid prolonged or repeated contact with the skin and wash thoroughly after use. Keep away from children, pets, and food.

© copyright 1999, P. A. Owen

UK gardening help and assistance