Overseed Bare Turf with Rolawn Seed and a Wolf-Garten Spreader Before Frost

Soil temperature, taken at 5cm depth with a cheap probe thermometer, is the single number that decides whether overseeding works. Rolawn Medallion and similar ryegrass blends want soil sitting between 8C and 12C. In September across much of the UK and northern Europe, the ground still holds summer warmth while the air cools, leaving a two to four week window before the first ground frost shuts germination down. Seed put down after that point can sit dormant long enough for blackbirds, wet weather, and rot to take their share, while seed put down during the warm-soil window has time to knit into the sward before winter.

The Wolf-Garten WE 330 spreader, a common broadcast model, has a calibrated dial running from 1 to 25. For a fresh overseed on thin turf, most fine ryegrass blends call for 25 to 35 grams per square metre. On the WE 330, that usually means a dial setting around 18 to 22. Spreaders vary, so the reliable method is to weigh out seed for a measured 10 square metre strip, push the spreader over it at normal walking pace, and check what remains in the hopper. Adjust and repeat until the strip takes the planned amount. Two lighter passes at right angles produce a more even result than one heavy pass, since a single run can leave stripes.

Compacted Clay Under New Seed

Grass seed germinating on compacted clay is trying to root into a sealed surface. The roots hit a pan, water sits in a skin on top, and young plants may drown during a wet spell or dry out during the next dry week. Clay soils across much of Britain, especially the heavy Weald and Midlands clays, drain slowly enough for autumn rain to stand on the surface for days.

Aeration before sowing pays for itself in root space. A hollow-tine aerator, either a manual fork model or a hired petrol machine such as those from HSS Hire, removes plugs of soil and leaves open channels. On a lawn under 100 square metres, a hand tool such as the Yard Butler coring aerator can do the work in an afternoon, although it is awkward work. The plugs can be left to break down or raked off before dressing.

Top dressing matters most on clay. A sandy loam dressing works, as does a home mix of sharp sand and sieved compost at roughly two parts sand to one part organic matter. Brushed into the tine holes and over the surface, it opens the top layer over successive years. The change is only a few millimetres per season, and a heavy clay lawn may need three or four autumns of dressing before it feels different underfoot. Claims of a one-season cure sell optimism.

Worm activity can do more for clay drainage than most mechanical work. Earthworms pull organic matter downwards and leave vertical burrows for water to follow. Overuse of moss killers and some fungicides suppresses them, so a chemical chase for a perfect green surface can weaken the biology that improves drainage.

Iron Sulphate and Moss

Moss colonises where grass struggles, often in shade, compaction, poor drainage, acidic soil, or all of these together in the shadow of a north-facing fence. Iron sulphate, sold as sulphate of iron or ferrous sulphate, blackens moss within days by acidifying its cells. A typical rate is 15 to 20 grams per square metre, dissolved in water and applied with a watering can fitted with a fine rose, or used in granular lawn sand mixes.

The blackened moss still has to come out. Scarifying with a spring-tine rake suits small areas, while a powered scarifier is better for larger lawns. In the same autumn window as overseeding, the sequence is efficient: iron sulphate, scarify once the moss blackens, aerate, dress, then sow into the opened turf.

Iron also greens grass by supplying available iron, which is why football pitches get regular applications. A chemical moss treatment leaves the cause untouched when shade or drainage remains, and the moss returns by spring.

Feeding the Soil Beneath the Grass

Worm castings are one of the most concentrated soil conditioners a garden can produce. A wormery turns kitchen scraps into castings without smell when it is run properly.

A tiered wormery, such as those from Wiggly Wigglers or the Worm Cafe, houses Eisenia fetida, the brandling or tiger worm. These worms process soft vegetable waste, coffee grounds, and torn cardboard. The castings that gather in the lower trays are dark and fine enough to sieve into a lawn dressing at a handful per square metre.

Leaf mould is the other autumn resource, and patience is the main cost. Fallen leaves raked into a wire bin, or packed into a black bin bag with a few holes punched through it, break down by fungal action over 12 to 24 months. Oak and beech leaves take longer than lighter leaves such as birch or hornbeam.

After one year, leaf mould is usually a rough mulch. After two years, it can become fine enough for seed-sowing medium or lawn dressing. It contributes little nutrient compared with compost, yet it holds moisture and improves structure, which is exactly what the top few centimetres of a clay lawn need.

Bokashi works faster because it ferments food waste, including cooked scraps and small amounts of meat that a conventional heap struggles with. A bokashi bin uses bran inoculated with effective microorganisms. The method is simple layering: a few centimetres of waste, a sprinkle of bokashi bran across the whole surface, firm pressure to exclude air, then a sealed lid. The process repeats until the bin is full, followed by two weeks for fermentation to finish.

Bokashi output is a pickled, acidic pre-compost that needs burial in a trench or addition to a conventional heap before it breaks down fully. Buried directly under a planned seedbed a month before sowing, it gives soil biology time to neutralise the acidity before seed goes in.

A wormery and a bokashi bin can support the same lawn cycle. Once the sharpest acidity has passed, fermented bokashi output becomes worm food, and Eisenia fetida process it quickly because the breakdown has already begun. The castings then return to the lawn dressing, turning a kitchen caddy into soil material over the year.

Two Weeks of Aftercare

Seed left dry after sowing becomes expensive bird feed. The surface needs to stay consistently moist, never waterlogged, for the first ten to fourteen days. In dry spells, light watering once or twice daily with a sprinkler on a timer keeps the surface film that ryegrass needs to chit. Once seedlings reach 5 to 7cm, the first cut can be made with blades set high, taking off no more than a third of the leaf.

Foot traffic should stay off the area for the first fortnight. A single line of footprints across germinating seed can leave a bare mark for months. Netting, or a few garden canes and string, helps deter cats and the family shortcut. Weed and feed products should wait until the new grass has been mown three times, because the herbicide component can check or kill seedlings that young.

A 50 Square Metre Lawn

Take a back lawn of 50 square metres, with half of it thin and mossy under a fence. At 30 grams per square metre, the overseed takes 1.5kg of Rolawn seed, so a 2kg box covers it with some margin. Iron sulphate at 18 grams per square metre for the mossy 25 square metre half needs about 450 grams dissolved across roughly 20 litres of water. Hollow-tine aeration by hand is an afternoon of work. A top dressing at 3 litres per square metre across the full 50 square metres comes to 150 litres of sandy loam mix, equal to six 25-litre bags or a builder’s bag when dressing more heavily.

The work fits across a single week. Iron sulphate goes on first, followed by four days for the moss to blacken. Scarify and rake out the dead material, aerate, spread the dressing, then broadcast the seed with the Wolf-Garten spreader in two crossing passes. Water it in. The whole job is about two weekends of work and perhaps sixty pounds in materials, mostly dressing and seed.

When Frost Arrives Early

Some autumns close early. A hard ground frost in the first week of October, which occurs in colder inland and upland gardens, can end the germination window before slower gardeners have started.

If frost arrives before the seed is down, store it dry and sealed for spring. Ryegrass keeps its viability for two to three years in a cool dry cupboard. Bare patches also need to be traced back before the next autumn if they came from drainage, shade, or wear, because sowing into unchanged conditions can produce the same thin turf and the same disappointment the following September.

The awkward evidence remains in the lawn itself: bare ground can be a seed problem and a soil problem at the same time.