When and how to feed your lawn

Do you need to feed at all?

Start with a sceptical question. The RHS says poor lawns may need feeding, but advises carrying out spring, summer and autumn maintenance first so the grass can thrive on its own. It also says most lawns do not need regular feeding to stay green and healthy, and that most UK soils feed plants adequately.

That does not mean never. A thin, pale lawn that is growing slowly, a lawn recovering from heavy scarifying, or one that has been cut short for years may well respond. The sensible approach is to treat feeding as a tool you use when the grass is struggling, with the smallest amount that does the job, rather than a fixed calendar chore.

What the N-P-K numbers on the bag mean

Every fertiliser label shows three nutrients as a ratio: nitrogen (N), phosphorus (P) and potassium (K). The RHS describes nitrogen as supporting growth of leaves and stems, phosphorus as supporting root and shoot development, and potassium as supporting flowering, fruiting and cold hardiness.

For a lawn, that translates into a simple pattern. A feed with a high first number pushes green leafy growth, which is what you want in spring. A feed with relatively more phosphorus and potassium puts less emphasis on top growth and more on roots and toughness, which is what you want going into winter. This is why the RHS separates spring and summer lawn fertilisers from autumn ones.

Quick release or slow release

The RHS notes that inorganic fertilisers are usually more concentrated and act faster, while organic ones are less concentrated and act more slowly. Some inorganic granules are coated, for example in sulphur, wax or resin, so they release nutrients gradually as they take up water. Liquid feeds generally act quickly.

Its spring and summer lawn advice recommends a specific spring and summer lawn fertiliser that is high in nitrogen and releases slowly over several months, so only one application is needed. As general guidance, a quick-release feed gives a fast colour boost but is easier to overdo and can give a flush of growth followed by a lull. A slow-release product is more forgiving if your spreading is not perfect.

The feeding year

Spring. The RHS says to apply a spring and summer feed in mid-spring while the lawn is actively growing, usually late March to April. Use the manufacturer's rate, spread evenly, in cool, moist conditions when rain is expected, or water it in lightly afterwards.

Summer. The RHS says that if the lawn still looks poor after a couple of months you can feed again, but not after August. Its fertilisers page also says summer lawn feeds go on when the soil is moist and the grass is growing. If it is hot and dry, wait. The grass is not using nutrients properly and you are risking scorch.

Autumn. The RHS says autumn lawn fertilisers go on from September, while the soil is moist, until mid-October, ideally before the first frosts. An autumn feed is higher in potassium and phosphorus to build hardiness and root growth. The RHS is explicit that you should not use leftover summer feed in autumn, because it is high in nitrogen and encourages lush growth that is prone to disease at that time of year. It also notes that most lawns recover from summer stress without any feed at all.

How to apply a feed evenly

Streaks are the usual result of guessing. Weigh out the rate on the packet for the area, which you can work out by measuring the lawn. The RHS gives a rough guide of about a handful per square metre for autumn feed, but always follow the pack for your product.

Then split the dose. As general guidance, put half in one direction and the other half at right angles, so any gaps in the first pass get covered by the second. A drop or broadcast spreader is much more reliable than hand scattering on anything bigger than a small patch. Keep granules off paths and borders, and sweep spills back onto the grass.

Timing against the weather matters. The RHS advises applying just before forecast rain, and watering it in if no rain comes within a day or so. As general guidance, avoid frosted, waterlogged or baked ground.

What not to do

• Do not feed in a drought. The RHS says not to apply lawn weedkiller or fertiliser to drought-affected turf in autumn, and to wait until spring if needed. Brown grass in a dry spell is usually dormant, not hungry.
• Do not double up. The RHS warns that incorrect application and overuse can cause pollution, and that excess nutrients harm soil health. As general guidance, a heavy hand also burns grass and pushes soft growth.
• Do not feed late. The RHS puts the end of the autumn window at mid-October, and the end of the summer window at August.
• Do not feed a wildflower patch. The RHS says areas you are encouraging to become wildflower patches should not be fed.

Weed and feed: use with caution

Combined weed and feed products are widely sold, and some lawn care firms include them in routine visits. The RHS says they reduce lawn biodiversity and are often unnecessary, because most lawns do not need regular feeding and weeds can be removed with non-chemical methods. It also warns that clippings from lawns treated with selective weedkillers can damage other plants if added to compost.

The RHS pages we read do not say how long to wait after a weed and feed before sowing seed. Check the product label before you overseed. As general guidance, if you plan to overseed, choose a plain lawn feed and deal with weeds by hand rather than risk a herbicide residue near new seedlings.

How feeding fits with scarifying and overseeding

Order matters. The RHS October advice is to apply an organic autumn feed after scarifying and aerating, if the grass is growing poorly. As general guidance, feeding a thatchy, compacted lawn mostly feeds the thatch. If you are working through the whole sequence, our autumn lawn restoration timetable shows where each job sits.

For a new lawn from seed, the RHS gives 70g per square metre (2oz per square yard) if you rake in general-purpose fertiliser before sowing. For patching an existing lawn, read our guide to overseeding step by step first. If you would rather have the whole programme planned and carried out for you, our lawn maintenance service covers it.