Lawn Care Guide: What to Do Every Month of the Year

Which grass do you actually have?

Almost every northern lawn is a blend of three or four species rather than one. Which species dominates decides how high to mow, how much feeding the lawn needs and how it behaves in a dry August. That is why two neighbours can follow identical advice and get different lawns.

Look at the turf in June, when everything is growing. You don't need to identify every blade, only to see which type is winning.

A fescue-heavy lawn is a drought-tolerant lawn that prefers less nitrogen and a higher cut. A bluegrass and ryegrass lawn takes wear far better but needs more water and more feeding to look the part. Pale green patches that turn brown in early July are usually annual bluegrass, an unwanted annual that dies in heat, and the cure is a thicker lawn rather than a spray.

Worth knowing. Match the seed to the site rather than buying one bag for the whole garden. A shaded strip along a north wall wants a fine fescue blend; the patch where the children play football wants ryegrass and bluegrass. Sowing the same mix everywhere is why some parts of a lawn never catch up.

Why the calendar lies and the soil thermometer doesn't

Grass does not know it is April. It starts growing when soil temperature settles above about 5 °C (41 °F), and seed does not germinate in earnest until the soil holds 10–18 °C (50–65 °F), however diligently you water. Soil lags behind air temperature by several weeks in spring, which is exactly why so much spring effort is wasted.

Three practical consequences follow.

1. Wait for growth before the spring feed. The simple test: you have mown once and the grass has grown back within a week. Feed earlier and much of the nitrogen moves past the roots before they can use it.
2. Seed into warm soil, not warm air. Late summer beats spring almost every year in zones 3–6, because the soil is still warm while nights have turned cool and dew has returned.
3. Get the autumn feed down while the grass is still growing. The roots need to take it up and store it. Applied after growth has stopped, it simply sits there.

A cheap soil thermometer pushed 10 cm (4 in) into the ground removes the guesswork. If you don't have one, the grass itself will tell you: when it visibly grows between two cuts, the soil is warm enough.

Zone table: the lawn year in zones 3–6

These are approximate timings in an ordinary year. Weather always beats the calendar, and a cold spring can push everything back two or three weeks.

Common mistake. Treating September as the autumn feeding month everywhere. In zone 3 the window has usually closed by mid-August. A late application does nothing useful for the roots but does leave soft growth going into the first hard frost, which is what snow mould feeds on.

How high should you cut the grass?

Mowing height is the single most important setting in the whole lawn year, and the one most often wrong. A grass plant roots roughly as deep as it stands tall. Cut to 3 cm (just over an inch) and you get a root system that dries out in the first heatwave and can't reach nutrients further down.

Aim for 6–9 cm (2.5–3.5 in) as your standard. Raise it to 9–10 cm (3.5–4 in) during hot spells and in shaded areas, where the plant needs more leaf area to live on less light.

The one-third rule is the other half of it: never remove more than a third of the blade in a single pass. If you want a 7 cm (3 in) lawn, mow when it reaches 10 cm (4 in). If the lawn hit 15 cm (6 in) while you were away, bring it down over two or three cuts a few days apart rather than scalping it in one go.

Leave the clippings when they are short and dry. Every bag you carry away takes nitrogen the plants drew out of the soil, and a lawn that keeps its clippings needs measurably less fertiliser than one that is always collected. Do bag it when the grass is long, wet or full of weed seed, or the clippings settle in mats that smother what is underneath.

Blade sharpness matters too. A dull blade tears rather than cuts, and the ragged tips dry out and go grey. If the lawn looks hazy and greyish a day after mowing, that is nearly always the blade rather than drought. Sharpen or replace once a season.

Feeding: three applications and a budget in pounds

Feeding advice usually stops at "fertilise a few times a season", which helps nobody standing in front of a shelf of bags. Work in nitrogen instead, and read the first number in the NPK ratio. A bag marked 11-3-5 is 11 % nitrogen, so 1 kg of product carries 110 g of nitrogen.

Two figures are worth memorising:

• No more than 0.5 kg nitrogen per 100 m² (1 lb per 1,000 sq ft) in one application. Above that you risk scorching in heat and losing the surplus to run-off. With an 11 % product that works out at roughly 4.5 kg per 100 m² (9 lb per 1,000 sq ft).
• 1–2 kg nitrogen per 100 m² (2–4 lb per 1,000 sq ft) per year. The lower figure suits a low-input fescue lawn that mainly needs to be green and alive. The higher figure suits a hard-used bluegrass and ryegrass lawn.

The autumn feed repays the most effort. Potassium hardens cell walls, the low nitrogen keeps the plant from pushing soft growth into frost, and the roots bank energy that gets paid back as an early green-up next spring. If you can only manage two applications, drop the summer one.

Always spread onto dry grass and water in with 5–10 mm (0.2–0.4 in) if no rain is forecast within a day. Uneven spreading shows as dark green stripes for months, so if you're spreading by hand, put down half the rate walking one way and half walking across it.

Feeding in the middle of a dry spell. The plant cannot take up nutrients without water, and the salts in the fertiliser pull further moisture away from the roots. Wait for rain and the same bag does twice the good.

How much water does a lawn really need?

An established lawn needs roughly 25 mm (1 in) of water a week during dry weather, rain included. A millimetre is the same as a litre per square metre, so a 100 m² (1,075 sq ft) lawn drinks about 2,500 litres (660 gallons) in a dry week. That is far more than most people assume, which is exactly why watering usually falls short: twenty minutes every evening delivers a fraction of it.

A little water often is worse than a lot rarely. Shallow watering keeps the moisture in the top few centimetres and the roots follow it upwards instead of chasing it down. The next time you go away for a week, the lawn turns brown.

1. Measure what your sprinkler actually delivers. Put three straight-sided tins out in the spray and run it for thirty minutes. Measure the depth with a ruler.
2. Convert to a full week's worth. If you collected 8 mm in half an hour, you need a little over 90 minutes to reach 25 mm. Note the time once and stop guessing for the rest of the summer.
3. Water once a week, not every evening. One long soak that reaches 10–15 cm (4–6 in) down drives roots deeper. Split it into two passes if water starts running off heavy clay.
4. Water in the morning. The blades dry during the day, which reduces disease pressure, and less is lost to evaporation than at midday.

One more thing worth saying plainly: a brown lawn in July is usually not a dead lawn. Cool-season grasses go dormant in drought, look terrible for three weeks and come back when the rain does. If you are under a watering restriction, letting that happen is a perfectly reasonable choice. Raise the cut to 9 or 10 cm (3.5–4 in), stop feeding, and keep foot traffic off the dry turf.

Spring: March, April and May

March

Stay off the lawn while it is frozen or waterlogged. A footprint in saturated soil compacts the ground for years and becomes the first place moss moves in. Wait until the surface carries your weight.

Once it does, rake off leaves, twigs and winter debris with a leaf rake, gently. This is tidying rather than dethatching, just enough to let light and air reach the base of the plants. Grey, matted patches are snow mould, and those areas need loosening and then overseeding once it warms up.

In zone 6, March is also when soil temperature approaches the 13 °C (55 °F) mark where crabgrass germinates. If you use a pre-emergent, that threshold is the trigger, not a date on the bag. Note that a pre-emergent will also stop grass seed, so you cannot do both jobs in the same area in the same spring.

April

Take the first cut when the grass reaches 9–10 cm (3.5–4 in). Don't go below 7 cm (3 in) on that first pass even if you plan to run lower in summer. The plant has just woken up and doesn't need the stress.

The spring feed goes down after the first or second cut, once growth is obvious. If a soil test puts you below pH 5.5, lime now instead and push the feed back a few weeks. Lime and fertiliser should not go on together.

May

May is when everything grows at once, and the commonest reason a lawn slips is simply that mowing falls behind. Cut once or twice a week. The one-third rule still applies.

May is also the right moment for dethatching if the thatch layer calls for it, and for patching thin areas in zones 5 and 6. The soil is warm and the grass is growing hard enough to knit back quickly. Sow 0.5–1 kg per 100 m² (1–2 lb per 1,000 sq ft) into the gaps, cover with 2–3 mm of fine topdressing and keep the surface damp for two to three weeks.

Worth knowing. If you have bulbs naturalised in the grass, don't mow those areas until the foliage has yellowed on its own, roughly six weeks after flowering. That matters most for daffodils, which build next year's flower inside this year's leaves. Our guide to choosing bulbs covers which ones take to rough grass and which sulk.

Summer: June, July and August

June

Growth is still strong and mowing has to keep pace. Check your cutting height now and lock it in for summer. If June turns dry, go up a notch straight away rather than waiting for the lawn to brown.

June is the last sensible month for major repairs before the heat arrives. After midsummer, new seed is an unreliable investment in zones 5 and 6.

July

Mow less often and higher. Nine to ten centimetres (3.5–4 in) in hot, dry weather shades the soil, slows evaporation and keeps weed seed from germinating in the gaps.

The summer feed goes down mid-July at half rate, and only if the lawn is being watered. In drought or under restrictions, skip it entirely. No lawn has ever suffered from a missed summer feed, while plenty have been scorched by a badly timed one.

Common mistake. Trying to rescue a heat-stressed lawn with fertiliser. Brown in July is dormancy, not hunger. Nitrogen pushes the plant to grow when it has no water to grow with, and the result is weaker roots and a slower recovery in August.

August

Late August is when the year turns. Nights cool, dew returns and the soil is still warm. That is the best combination all year for sowing grass: warm soil for fast germination, cool air so the seedlings don't fry.

If the lawn is thin, worn or patchy after summer, this is when you fix it — not next spring. In zone 3 that work starts in late July; in zone 6 it runs into mid-September.

Autumn: September, October and November

September

For most of zones 4 to 6, September is the most important month in the lawn calendar. Three jobs belong here, in this order:

1. Aerate if the soil is compacted. A core aerator that pulls plugs works far better than spiking on clay and on hard-walked routes. Leave the plugs on the surface to break down.
2. Overseed the thin areas. Scratch the surface open, sow 0.5–1 kg per 100 m² (1–2 lb per 1,000 sq ft), topdress 2–3 mm and keep it evenly moist until the seed is up.
3. Apply the autumn feed. Low nitrogen, high potassium, no later than the date for your zone. If you have just seeded, wait until the new plants have been mown twice.

Keep mowing as long as the grass grows. Autumn mowing is the job people forget, but grass that goes into winter long lies flat under snow and makes an ideal home for snow mould.

October

Leaves are the main threat this month. A layer of wet leaves left for two weeks shuts out the light and leaves yellow patches that show all through the following year. Rake them, or run the mower over them so they are shredded fine enough to drop between the blades — shredded leaf litter is genuinely good for the soil, whole leaves sitting in mats are not.

If moss is a problem, iron sulphate can go on now, but read the moss section below first. Moss is a symptom, and iron sulphate treats only the symptom.

November

Take the final cut when growth has all but stopped, at 5–6 cm (2–2.5 in). Not shorter, because the plant loses leaf area it needs, and not longer, because it will lie flat.

Clear the last of the leaves, move furniture and trampolines off the turf, and drain the irrigation before the first hard freeze.

Winter: December, January and February

Winter is mostly about not doing damage.

Keep off frozen grass that has no snow cover. The blades are stiff with frost and snap underfoot, and the brown tracks stay visible until May. Don't pile shovelled snow in one spot, because the ground under a heap goes waterlogged and airless as it melts, and never salt a path along the edge of the lawn.

An ice crust that sits for several weeks is the one thing that genuinely kills patches of turf, because the grass suffocates under the sealed layer. If ice is still sitting there in February you can break it up carefully in the worst places, but don't dig into the frozen surface.

February, on the other hand, is a good month to service the mower, sharpen the blade and order seed. Having seed in the shed in March means you can sow at the right moment rather than three weeks after it.

Moss, thatch and dethatching

Moss doesn't invade. It arrives because the grass has already given up in that spot. Five causes cover almost every case:

Iron sulphate blackens moss within days and makes it easy to rake out. It cures nothing. Remove the moss without addressing the cause and it is back within a year, and in the meantime you have opened the surface to weed seed. Always pair moss removal with overseeding, or something else will fill the gap.

Thatch is a different thing: a layer of dead and part-decomposed stems between the green growth and the soil. A thin layer is useful and springs underfoot. Once it passes about 1.3 cm (0.5 in) it starts shedding water and locking out nutrients, and that is when dethatching earns its place.

1. Measure the thatch first. Cut out a small wedge with a spade and look at the brown layer between green growth and soil. Under 1.3 cm (0.5 in), leave it alone.
2. Pick a moment when the grass is growing hard. Late spring is best, early autumn second best. Dethatching in October leaves a torn lawn with no time to recover before winter.
3. Set the blades to just tickle the thatch. Not into the soil. Make one pass rather than a cross-hatch if you are unsure.
4. Rake out every scrap, then overseed immediately. A dethatched lawn is an open seedbed, and open seedbeds fill with whatever gets there first.
5. Water and feed lightly. Keep the surface damp for two to three weeks while the new seed germinates.

When is a lawn the wrong answer?

Some areas will never carry decent turf no matter how well you look after them. Dry shade under a large conifer or maple is the clearest example: the tree takes both the light and the water, and the grass loses that contest every year. The same goes for steep banks that bake dry and are unpleasant to mow, and for narrow strips between paving where the mower doesn't fit.

The honest answer there is to stop. Ground cover plants handle dry shade far better than grass, need no mowing and look better in September than thin turf ever will. Under trees, perennials for shade also outperform a lawn that is permanently sparse.

If you want less lawn for other reasons, you can turn part of it into a planted bed, or let a corner grow taller and flower. An area cut every three weeks instead of every week quickly becomes one of the best places in the garden for bees and butterflies, especially if you sow bee-friendly plants into it.

You don't have to choose between tidy and wild. Plenty of gardens keep a closely cut area near the house where furniture and children need space, and a taller, less frequently cut area further out. A mown edge between the two is what makes the long part read as deliberate rather than forgotten.

Common mistakes

• Cutting too short. Three or four centimetres gives shallow roots, heat stress in July and an open surface where moss and weeds establish. Raise the cut and a surprising number of other problems solve themselves.
• Taking half the blade off at once. The plant responds by pushing new leaf at the expense of roots. After a holiday, bring it down over two or three cuts a few days apart.
• A little water every evening. It keeps roots shallow and makes the lawn more vulnerable, not less. One long soak a week beats seven short ones.
• Dethatching in autumn. A torn lawn in October goes into winter with open ground and no time to knit. Do it in late spring.
• Fertiliser without water. In drought the plant can't use it and the salts make things worse. Wait for rain.
• Killing moss without asking why it came. Iron sulphate removes the moss but not the shade, the compaction or the acid soil that produced it.
• Walking on frozen or waterlogged turf. Those tracks stay visible for seasons.
• Saving everything for spring. Late summer and early autumn are the best time of the whole year for seeding, aeration and the most valuable feed.

Frequently asked questions

How often should I mow the lawn?
By growth, not by day of the week. In May and June that often means once or twice a week; in a dry July it may be once a fortnight; in September it's back to weekly. The rule that governs everything is that you never remove more than a third of the blade in one pass. If you want a 7 cm (3 in) lawn, you mow when it reaches about 10 cm (4 in).

When should I fertilise a cool-season lawn?
Two or three times: a spring application once growth is under way and you have mown once, an optional half-rate summer application in mid-July if the lawn is watered, and an autumn application low in nitrogen and high in potassium. The autumn one matters most, and the cut-off moves with your zone — mid-August in zone 3, mid-September in zone 6. Keep every application at or under 0.5 kg nitrogen per 100 m² (1 lb per 1,000 sq ft).

Why is my lawn yellow and thin?
Read the pattern. An even pale wash across the whole lawn is usually nitrogen shortage. Brown patches in midsummer that recover with rain are drought, often combined with annual bluegrass. Yellow patches where leaves sat are light starvation. Grey matted patches in early spring are snow mould. A yellowish cast the day after mowing comes from a blunt blade.

When is the best time to seed a lawn?
Late summer to early autumn — late July in zone 3, into mid-September in zone 6. The soil is warm enough for fast germination while the air has cooled and dew has returned, which is exactly what seedlings need. Late spring is the second-best window. Seed does not germinate properly until the soil holds 10–18 °C (50–65 °F), so sowing too early in spring mostly feeds the birds.

How do I get rid of moss in the lawn?
Work out why it arrived first. Shade, compacted soil, a pH below 5.5, mowing too low and low fertility account for almost every case. Iron sulphate blackens the moss so it can be raked out, but without fixing the cause it returns within a year. Always rake out and overseed straight away, or the open ground fills with weeds instead.

Should I leave the grass clippings?
Yes, when they are short and dry. They are nutrients on the way back into the soil, and a lawn that keeps its clippings needs less fertiliser than one that is always collected. Do collect when the grass is long, wet or full of weed seed, because the clippings then sit in mats that smother the grass beneath and add to the thatch layer.

How short should the last cut before winter be?
Five to six centimetres (2–2.5 in). Shorter removes leaf area the plant needs to get through winter and opens the surface to moss. Longer and the grass lies flat under snow, stays wet for weeks and gives snow mould an ideal home. The timing is when growth has all but stopped, which can be late September in zone 3 and early November in zone 6.

Can a lawn that looks ruined be saved?
Almost always, and almost always without laying new turf. Start by raising the cut to 7 cm (3 in) and keeping it there for a full season. Aerate in early autumn if the soil is compacted, overseed the bare areas immediately afterwards, and put down an autumn feed. A very thin lawn takes two seasons, but the improvement usually shows after the first autumn.

If you'd like a reminder when the autumn feed and the overseeding window open in your zone, it goes out with our newsletter alongside the rest of the season's jobs.