The main types of weed killer
Garden weed killers sold for home use fall into a few broad groups. Knowing which group a product belongs to tells you how quickly it works and whether it will deal with the roots.
| Type | How it works | Speed | Best for |
|---|---|---|---|
| Contact | Damages the green parts it touches | Fast, often visible within hours to days | Young annual weeds, moss and quick tidy-ups |
| Systemic | Absorbed by leaves and moved down to the roots | Slower, typically one to several weeks | Established and deep-rooted perennial weeds |
| Path and hard-surface products | Formulated for patios, paths and drives; some also claim to slow regrowth | Varies by product | Joints between paving and gravel areas |
| Non-chemical methods | Physical removal, heat or boiling water | Immediate | Small areas, around ponds, or where you prefer to avoid chemicals |
Products change regularly and not all are approved for every situation, so read the label before you buy. It will tell you which surfaces the product is for, which weeds it controls, and how long to keep people and animals off treated areas.
Which weed killer is best for patios and paths?
For established weeds such as dandelions and docks
A systemic weed killer is usually the most effective option, because it reaches the roots. Weeds like dandelions have long taproots that regrow if only the leaves are removed. Apply when weeds are actively growing, typically from spring to early autumn, so they absorb the product well. Results take time; resist the urge to pull the weeds out before the product has worked through.
For young weeds and seedlings
A contact weed killer gives quick results on small annual weeds in paving joints. It may need repeating, because roots and new seedlings are not always affected.
For moss and algae on paving
Green growth on the surface of slabs is often algae or moss rather than weeds. A patio cleaner designed for moss and algae, or careful pressure washing, may be more appropriate than a weed killer. Our weed killer and patio cleaner range includes both.
For gravel paths and driveways
Gravel areas usually suit a path and hard-surface product applied with a sprayer or watering can fitted with a dribble bar, which gives even coverage with less drift.
How to apply weed killer safely and effectively
- Read the whole label. Check the dilution rate, coverage, weather requirements and re-entry times.
- Pick a dry, calm day. Rain soon after application can wash the product off, and wind can carry spray onto plants you want to keep.
- Wear gloves and suitable clothing; some products also recommend eye protection. See our workwear and PPE.
- Use a dedicated sprayer or watering can, labelled for weed killer only, so you never accidentally water plants with it.
- Apply only to the weeds and the hard surface, not to neighbouring lawns or borders.
- Keep children and pets away from the treated area for at least as long as the label states, usually until the product has dried.
- Rinse equipment as directed and store the product in its original container, locked away.
Protect drains and water: never apply weed killer onto or near drains, gullies, ponds or watercourses, and never pour leftover product or rinse water down a drain. Many hard surfaces drain straight into surface water. Follow the label for disposal of unused product, which may mean taking it to a local household waste site.
Non-chemical ways to clear patio weeds
Chemical treatments work best alongside good maintenance. Options that avoid or reduce chemical use include:
- Patio knife or weeding tool: drag along joints to remove weeds and the soil they grow in. Find these in our garden tools.
- Stiff brush: regular sweeping stops seeds settling in joints.
- Boiling water: poured carefully onto weeds in joints, it can kill top growth. Take great care to avoid scalds.
- Pressure washing: clears algae and loose joint material, but can wash out sand and loosen slabs. Refill joints afterwards. A suitable hose and attachments are in hoses and watering.
How to stop weeds coming back
Weeds grow in paving because joints hold soil, moisture and seeds. Once you have cleared an area, rake out the old joint material, sweep the surface clean and refill the gaps with a jointing compound or kiln-dried sand suited to your paving. Well-filled joints leave less room for seeds to settle. For gravel paths, a permeable weed membrane under the gravel helps, though seeds can still germinate in debris that collects on top, so rake and sweep regularly.
Treat little and often. A quick pass with a weeding tool every few weeks during the growing season is easier than tackling a patio full of established weeds once a year. Explore our weed control products to find a suitable option for your paving.