Suitable for...

The RHS believes that avoiding pests, diseases and weeds by good practice in cultivation methods, cultivar selection, garden hygiene and encouraging or introducing natural enemies, should be the first line of control. If chemical controls are used, they should be used in a only minimal and highly targeted manner.

Spot treatments

• Patio weeds are quick and easy to control with a ready-to-use spray gun
• Weeds in borders can often be treated individually (with caution and accuracy) using a ready-to-use spray gun, liquid concentrate or soluble sachet

Broad-scale weed treatment

• In an unplanted area, or where all plants are to be killed off, the most efficient and cost-effective method for treating larger areas of weeds is usually with a concentrate made up in a sprayer

When to apply weedkillers

Follow the advice given on the packet. Many weeds respond best to treatment when they are in full growth, and always apply on a calm day to prevent the spray drifting on to plant you want to keep.

How to apply weedkillers

The method of application depends very much on the individual products formulation. Here are some general guidelines:

Spot treatment

• Ready-to-use spray guns: Spray guns are an easy and quick way to spot-treat patio weeds. It is possible to use the narrow, jet setting on the spray gun to spot-treat weeds in garden borders. However, by twisting the nozzle, it usually allows you to adjust the spray type or to the spray width to your requirements. Some designs now come with an in-built pump action 
• Gel formulation: A gel preparation of glyphosate (Roundup Gel) makes for much more targeted treatment of weeds between garden plants
• Liquid concentrates and soluble sachets: These can be diluted and applied with a hand-held spray gun, available from most garden centres and DIY stores. Mark the spray gun for ‘weedkillers only’ and only make up as much as is needed. Rinse out the gun thoroughly at the end of the day. Do not store diluted product

Broad-scale weed treatment

• Where garden plants do not require protection (e.g. on an unplanted area), the most efficient and cost-effective method for treating larger areas of weeds is usually with a concentrate
• Dilute to the rate recommend on the label and apply either in a watering can or a sprayer. These should be kept specifically for the purpose of applying weedkillers and marked clearly to prevent accidental damage to plants or the environment

Link

Health and Safety Executive: home garden chemicals

Safety precautions

Always follow the dosing, application and health-and-safety instructions given on the label of the product concerned.

Although it is not a legal requirement to wear protective clothing when handling and using amateur/home pesticides, the RHS recommends wearing gloves, Wellington boots and other protective clothing as a sensible precaution.

Problems

Problems may arise when the instructions on the product are not followed and you may get weedkiller damage on desirable plants. Always read the label first for the best advice to help you get the most effective control.