Chemicals: using safely and effectively

Plants sometimes require protection from pests, diseases and competitive weeds. Consider non-chemical solutions first, but if you do decide to use chemical controls, keep it to a minimal and highly targeted manner, following the product instructions accurately to ensure that people, pets and the wider environment are protected. Here we guide you through the general principals of keeping you safe and minimising environmental harm.

Chemicals can be safely used in the garden by following a few common sense guidelines. Image: John Trentholm/RHS
Chemicals can be safely used in the garden by following a few common sense guidelines. Image: John Trentholm/RHS

Quick facts

Suitable for A wide range of pests, diseases and weeds
Timing Various, according to the problem
Difficulty Moderate

Suitable for...

Garden chemicals are used when it is not possible to control a problem through other methods. There are products legally available and sold for use on many pest, disease and weed problems that occur in the garden.

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 only used in a minimal and highly targeted manner. For example, where diseases or weeds pose a serious threat to the wider environment, to important heritage specimens, to habitat, or to native wildlife.

How to use chemicals safely

Many pest, disease and weed problems can simply be tolerated or managed by cultural methods such as picking off, squashing and digging out. Where these are not sufficient, other options such as biological control  can be highly effective. Where all these fail, you might consider using the garden chemicals products that are approved and sold legally to gardeners.

How do I use garden chemicals responsibly?

  • Always check labels for the ways in which a chemical product (including fungicides, insecticides or pesticides, herbicides or weedkillers, algae and mosskillers) can be used. Adhering to these instructions is a legal requirement. By reading the instructions before purchase, you can be sure you do not buy more than you need
  • Safety details on the label are to be followed
  • Rubber boots, old clothes or overalls and gloves, although not usually strictly necessary (and so are not stated on the labels), are a sensible precaution
  • Thoroughly rinse out old chemical containers before discarding 

Concentrates or ‘ready-to-use’?

Concentrates are mixed with water in a sprayer or watering can according to the instructions on the pack. They are useful where large areas or many plants need to be treated. It is important to only buy enough to treat the problem - if its a small job, ready-to-use products are a better choice.

Ready-to-use products are ideal for small areas or one off treatments. The bottle's nozzle design is adequate for treating a small area, although some now have pump action that can be used on a larger area.

There is a low health risk to gardeners from diluted chemicals and the slight hazard from the concentrates –  these are mitigated by following the instructions on the product.

Watering can or sprayer?

  • Ready to use products come in a sprayer and should be used in the sprayer provided
  • Sprayer or watering can use will be indicated on the label of concentrates
  • Have a dedicated sprayer for weedkillers and another for other chemical products
  • Sprayers and watering cans should be checked for leaks and blockages by using clean water before use
  • Where a measured amount of material is to be applied to a given area the output of the sprayer should be checked first using water alone

For garden chemicals and other plant protection products currently available to gardeners see:

Applying chemicals

When using a spray, consider the following;

  • Apply the chemical using a spray sufficiently coarse not to drift, but fine enough to cover the plants’ foliage evenly
  • Apply the chemical up to the given dosage per unit area or sufficient to wet foliage without run-off. Never apply chemicals on a windy day
  • After spraying, rinse the sprayer with three washes of a small amount of water, spraying this onto areas, plants or weeds listed on the label. The sprayer will then be safe to store

Safeguarding children and the environment

As well as measures to protect the operator and nearby plants, gardeners using chemicals are responsible for protecting children and wildlife, and avoiding pollution of the wider environment.

  • Exclude pets and children from treated areas until the spray has dried
  • Do not spray open blooms because of the danger to bees, butterflies and other flower visitors (pollinators)
  • Contamination of water must be avoided. Fish and other wildlife in ponds, ditches, streams etc, are very susceptible to chemicals. High risk activities include flushing surplus garden chemicals down toilets or drains, applying weedkillers to hard surfaces where run off might enter drains and emptying products on to the soil to dispose of them

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The Royal Horticultural Society is the UK’s leading gardening charity. We aim to enrich everyone’s life through plants, and make the UK a greener and more beautiful place.