It is best to reseed any dead spots quickly before weeds can get established in the bare soil. May and the period from mid-August to mid-September are good times to sow seed. For best results, you need to be able to count on 6 to 8 weeks of relatively warm (15 to 25°C) and humid weather after seeding.
Before seeding, take a careful look at your site and ask yourself about its limitations and how you intend to use it: Is it in the shade or the sun? Will it be used as a play area or be walked on frequently? These considerations will help you decide what mixture to use.
Some good seed mixtures
The standard mixture is Kentucky bluegrass (40 to 50%), creeping red fescue (30 to 40%) and perennial ryegrass (20%).
For dry sites, choose a mixture containing large amounts of creeping red fescue (60 to 65%), Kentucky bluegrass (20 to 25%) and perennial ryegrass (15 to 20%). For wet sites, replace the fescue with rough bluegrass (Poa trivialis). Grass is not suitable for heavily shaded areas (less than 4 hours’ sun a day), and you should consider other types of groundcover instead.
Play and foot traffic areas
Lay sod and reseed frequently with perennial ryegrass. Consider laying concrete slabs or natural stone instead in heavy traffic areas.
When you go to buy your seed, check the label to be sure you get the right mixture and germination percentage (at least 75%). Choose certified seed (Canada No. 1), to avoid growing weeds. Don’t try to keep seed from one year to the next, as old seed is less likely to germinate.
For best results:
- Remove any weeds and lightly rake the soil surface to loosen it.
- Sow the seed (by hand or using a broadcast spreader) as evenly as possible. The ideal density is 6 to 8 seeds per cm2.
- Lightly rake the surface (in one direction) to shallowly cover the seeds with 1 cm of soil.
- Gently firm the soil, by going over it with a lawn roller half-filled with water or by walking on it, to ensure that the seed adheres to the soil.
- Water the surface with a fine spray so as not to uncover the seed. Water frequently but in small amounts. Keep the soil moist for the first 2 to 3 weeks. Gradually increase the amount of water and reduce the frequency of watering as the roots grow. Avoid walking on the new grass.
- Once the grass is 5 cm high, it should be lightly rolled to even out the soil.
- Mow the lawn for the first time once the grass is 8 cm high. Cut it back only to 5 cm (no shorter).