Grass Seed in Ireland

September, by a clear margin. The soil still holds summer warmth so seed germinates in a week to ten days, autumn rain arrives to keep it moist without you having to water, and the annual weeds that would compete in spring have finished for the year. The grass then has all autumn to root before growth stops. April and May are the second window and work perfectly well, but a spring sowing has to compete with every weed seed in the ground and can be caught out by a dry May. Avoid June and July, when a dry spell will kill a new sowing faster than you can water it.

For a brand new lawn on bare soil, 35g per square metre. For overseeding an existing lawn or patching thin areas, 25g per square metre is enough because the established grass fills in around it. That means a 1kg box covers roughly 28 square metres of new lawn or 40 square metres of overseeding. Resist the temptation to sow heavier than the rate on the bag: seedlings sown too thickly compete with each other, and the resulting turf is weaker and more prone to disease than one sown correctly.

Grass seed needs a soil temperature of around 8 to 10C to germinate, and in most of Ireland that means the door closes through October. Seed sown in late September in Munster or coastal Leinster will usually still get away. Sown in late October in the midlands or the north west it will sit in cold wet soil, rot or be eaten, and you will have wasted the money. If you have missed the autumn window, prepare the ground over winter and sow in April instead.

Seed costs a fraction of turf, gives you a real choice of mix, and produces a lawn with a better root system because the grass establishes where it grows. Turf gives you an instant green surface, which matters if you have children or dogs and cannot fence the area off for two months. In Irish conditions the practical difference is timing: turf can be laid through most of the year provided it is watered, while seed is tied to the sowing windows. For most gardens seed is the better value, and September sowing narrows the establishment gap considerably.

Almost always shade, compaction or wet ground rather than anything wrong with the grass itself. Moss thrives in exactly the conditions an Irish winter provides and it colonises any gap the grass leaves. Killing the moss without changing the conditions just resets the clock. Look at what is causing the gap: is the area under a tree or a north facing wall, is the soil so compacted that water sits on it, is the mower set too low, has the lawn been fed in the last two years? Fix that, then overseed the bare ground in September with a shade tolerant or fescue rich mix.

Not at sowing time on decent soil, and never with a high nitrogen feed on a lawn under two months old. Use a pre-seeding fertiliser with phosphate before you sow if the ground is poor, since phosphate drives root development. After that, the standard Irish routine is a spring feed in March or April to push growth after winter, and an autumn feed high in potash in September or October to harden the grass for winter. Skip the autumn feed and you get a soft sward that moss walks into over the wet months.

You can, but be honest about how much shade there is. Shade tolerant mixes based on hard fescue and creeping red fescue will hold on under high canopy or the dappled shade of a birch. Under dense evergreen conifers, or where the soil is bone dry from tree roots taking all the water, no grass mix will succeed and repeated sowings just waste seed. In those spots a shade tolerant ground cover planting or a bark mulched bed is the answer, not more grass seed.