When working with weed killers, it is essential to work carefully to minimise any possible risk of harm to the user or to the environment. Always wear protective clothing when mixing or applying chemicals, and never work in windy weather when there is a risk of spray being blown back to you or across to nearby plants. You should also carefully follow the instructions for disposal of excess chemicals; they should never be poured down sinks, drains or watercourses. Our section on Safety in the Garden has a feature on Chemical Safety, with a range of useful tips for storing, working with and disposing of weedkillers and other garden chemicals.

Working with Weedkiller

There are many ready-to-use weedkillers available, which come with their own spray head attached. These are convenient to use and save you from having to handle the chemical. However, for larger areas it may be more economical to buy a concentrate to dilute yourself; you will also need your own equipment such as a sprayer or watering can set aside just for this purpose. Some weedkillers, such as weed preventers, are applied as granules.

Always read and follow the instructions on the packet when using weed killers. If you are using chemicals to clear and replant an overgrown area, make a note of how long you will need to leave the ground before you are able to replant. Chemicals such as glyphosate do not persist in the soil for long, and so the ground may be re-used with a few weeks. Other products may need to be left for longer; any ground treated with sodium chlorate-based weedkillers should not be re-planted for six months.

The best time of year to apply a systemic weedkiller, such as glyphosate, is in late spring when the plant has started to grow and the plant's transport system is active. It is often worth cutting back large perennial weeds like bramble a few weeks before spraying so that they produce healthy new foliage that will take in the weedkiller better. Some weeds have a waxy coating that repels liquids; these can be made more receptive by beating their foliage with a stick to bruise it.

Always apply weed killer exactly as directed on the packet, and make sure that you wear protective clothing such as goggles and rubber gloves. If you need to treat weeds that are amongst garden plants you must take care only to treat the weed; consider using a paint-on version rather than a spray, or cover nearby garden plants with cardboard boxes while spraying.

After applying weedkiller, be patient, as it may take several weeks before the weed shows signs of dying. Re-apply the product if new growth appears, and then dig out and remove dead weeds.