A lawn is the most patient part of your garden. But when it comes out of winter looking pale, turns strawy in high summer, or lets moss crowd out the grasses, the cause is almost always the same: its nutrient supply. Feeding a lawn is no black art, but it follows a rhythm. Three doses a year, each with a different job. And the most important one is not in spring but in autumn.
What the grasses actually need
Every fertiliser bag carries three letters: N, P and K, the three main nutrients. Each does a different job.
Nitrogen (N) is the engine of growth. It drives the deep green and makes the grasses branch densely. Too little, and the lawn turns pale and thin. Too much, and it grows soft and becomes prone to fungi. Nitrogen is the nutrient people get wrong most easily.
Phosphorus (P) looks after the roots and matters most for young, freshly sown or turfed areas. An established lawn usually gets by on little phosphorus.
Potassium (K) is the quiet hero. It sits in the cell walls, regulates the water balance, and makes the grasses firm and resilient. Potassium is why a well-supplied lawn shrugs off drought and does not heave so easily in winter. That is exactly why the autumn dose revolves around this element.
The three doses through the year
A healthy lawn does not get its annual nitrogen all at once, but in portions. Roughly speaking, most utility lawns need about 20 to 30 grams of pure nitrogen per square metre per year. Applied in one go, that would be an overdose. Split across three dates, each dose gets its own role.
- Spring · around CW 12
The starting gun after winter. A moderately nitrogen-led feed wakes the grasses, fills the gaps and pushes the moss back. Not too early: the soil has to have woken up.
- Summer · around CW 24
The maintenance dose. It carries the lawn through the growing phase and the summer stress. A slow-release fertiliser hands out its nutrients over weeks instead of all at once.
- Autumn · around CW 38
The key dose. A potassium-rich autumn feed with little nitrogen readies the grasses for winter and makes them frost-hardy.
Spring: the start, but not too early
The first dose falls around CW 12, the second half of March. But the exact timing depends on the soil, not the calendar. Grasses only start growing once the soil temperature stays above roughly 8 to 10 degrees. A good marker: once the forsythia is in bloom, the soil is ready.
Feed too early, while it still frosts at night, and the grasses cannot take up the nitrogen at all. It washes out and is lost; better to wait a week longer.
For the spring start a fertiliser led by nitrogen works well, ideally a slow-release one, so the grasses get going evenly rather than shooting up in a single flush. If your lawn is mossy, it makes sense to pair the spring feed with scarifying: feed just before or after scarifying so the grasses close the new gaps quickly.
Summer: the calm maintenance dose
Around CW 24, mid-June, the lawn is in full growth. Now it is not about a boost but about holding on. The summer dose replaces what frequent mowing and watering take away, and keeps the surface dense enough that weeds and clover cannot get a foothold.
A slow-release fertiliser really pays off here. It hands out its nutrients over six to ten weeks and so bridges the holiday season and the heat spells.
If you prefer things organic, summer is a good time for organic or organic-mineral fertilisers. They act more slowly, but they barely scorch and they feed the soil life along the way.
Mowing is a small feed. If you mow regularly and leave the fine clippings lying (mulch mowing), you return part of the nutrients straight to the soil. That replaces none of the three doses, but it noticeably lowers the demand. Important: only fine clippings may stay; thick mats of grass smother the lawn.
Autumn: the key dose of the year
Now comes the part many people skip. Around CW 38, the second half of September, the lawn gets its autumn feed, and it is different from the two before.
In autumn you no longer want to drive growth. You want to harden the grasses off. A classic autumn lawn feed is therefore potassium-rich and holds only a little nitrogen. The potassium moves into the cells, lowers the freezing point in the tissue like a natural antifreeze, and firms up the cell walls. That way the grasses go into winter resilient and are less prone to fungi come spring.
If you feed your lawn only once a year, do it in September. The autumn dose decides how the lawn comes out of winter.
Rule of thumb for autumn
The most common autumn mistake is simply to use up the leftover summer fertiliser. A nitrogen-led feed in September drives soft growth right before the frost, which the first cold snap catches. Buy a dedicated autumn or potassium fertiliser for the season, not an all-purpose one.
How to spread the fertiliser properly
Spread by hand, you almost always get stripes: where too much lands the lawn scorches; where too little lands it stays pale. A spreader solves the problem.
Mow and know your area
Mow one to two days ahead at normal height. Measure your area roughly so you dose the right amount; the bag states the grams per square metre.
Set the spreader
Set the spread rate to the manufacturer's figure. When in doubt, go lighter: topping up is easy, too much fertiliser cannot be taken back.
Work in lanes
Do the edges first, then the area in straight, slightly overlapping lanes. That leaves no gap and nothing gets double-fed.
Water and spare it
Water thoroughly after spreading if no rain comes. The granules have to move off the blades to the roots, otherwise they do nothing and can scorch the leaves in sun. Then keep off the area for a few days.
pH and soil: the foundation under the fertiliser
Fertiliser only works if the soil makes it available. Lawns like a slightly acidic to neutral soil, around pH 5.5 to 6.5. If the soil is too acidic, moss spreads and the grasses reach the nutrients less well, no matter how much you spread. A simple pH test strip gives you a bearing. If the value sits well below 5.5, a dose of lime in late winter helps, ideally kept separate from feeding.
Moss in the lawn, by the way, is rarely a nutrient problem alone. Usually compaction, shade, waterlogging or too low a cut lie behind it. Feeding and scarifying help, but only if the cause is treated too.
Common mistakes that cost you the lawn
A few things go wrong again and again. Avoid them and you are ahead of most.
- Feeding it all at once. One big spring dose scorches the lawn and washes into the groundwater. Three small doses are gentler and more effective.
- Nitrogen in autumn. Soft growth before the frost weakens the lawn. In autumn, potassium belongs in the spreader.
- Feeding a dry lawn in the heat. That scorches the blades. Better a cool, overcast day, and water in.
- Spreading by hand. It leads to stripes. A cheap spreader pays for itself on the first use.
Lawn care is a rhythm, not a one-off effort. Three well-timed doses and a little patience: that gives you a dense, deep-green lawn that gets better year after year.
Häufige Fragen
How often should I feed my lawn in a year?
Three doses a year is the tried-and-tested rhythm for a healthy utility lawn: in spring around CW 12, in summer around CW 24, and in autumn around CW 38. Each dose has its own job. Spring wakes the grasses, summer holds them, autumn hardens them off. If you can or want to feed only once, do it in autumn with a potassium-rich fertiliser, because that dose matters most for the lawn's health.
Why is autumn feeding more important than spring feeding?
Because it carries the lawn through winter. An autumn feed is potassium-rich and holds little nitrogen. The potassium firms up the cell walls and lowers the freezing point in the plant tissue, so the grasses take frost better and are less prone in spring to fungi such as snow mould. The spring dose only delivers the quick green start; the autumn dose lays the foundation for a whole year.
Can I feed my lawn in autumn with ordinary lawn fertiliser?
Better not. Ordinary lawn or all-purpose fertiliser is nitrogen-led and drives soft growth. Right before the first frost that is exactly the wrong signal: the young, soft blades freeze and weaken the lawn. Use a dedicated autumn lawn feed or potassium fertiliser with little nitrogen. Save the rest of the summer fertiliser for next spring instead.
When is the lawn ready for its first spring feed?
Not by the calendar, but by the soil. The grasses only take up nutrients once the soil temperature stays above roughly 8 to 10 degrees, usually from the second half of March around CW 12. A reliable sign: once the forsythia is in bloom and you have mown for the first time, the fertiliser can go out. Fed too early, the nitrogen just washes out and is lost.
Do I have to water after feeding?
Yes, if no rain comes. The fertiliser granules have to be washed off the blades down to the roots, otherwise they do nothing and can scorch the leaves in sun. The easiest way is to feed on an overcast day with rain forecast, then the sky does the watering. Otherwise give the lawn a thorough soak yourself after spreading.
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