Question
Hi,

I live in Toronto. I am relatively new to home ownership and caring for lawns. What is meant by overseeding and how is it done? Do you spread out fresh soil on top of sparse areas then sow seeds? Do you have to dig up spots?

Thanks for your time.

Answer
Overseeding simply means spreading grass seeds over an existing lawn. You can also call it reseeding when it is bare spots. Some people will spread grass seeds over an existing lawn to thicken it up.

For bare spots, I recommend digging the top few inches of soil loose. If you can mix in handfulls of compost (or potting soil) to improve the quality of the soil, you usually get better result with that. The "golden rule" is to put a 1-2" layer of compost over the area to be reseeded and dig it into the top 3-5" of soil. Then spread grass seeds thickly and firm down well. Water once really well to settle the soil, and then keep the seed bed consistently moist until the grass sprouts (never allow the seeds to dry out). This can be done by watering daily until grass is 2" tall. Then gradually over the next 2-3 weeks increase time between watering and the amount of water you apply.

The normal way to water a lawn is to water infrequently and deeply; if no rain (e.g. such as once per week for 2 hours). For seed establishment, however, you should never allow the lawn surface to dry out (or the seeds die). Water frequently and shallowly (such as twice daily for 10 minutes). Once the new grass is a few inches tall, you should gradually transition from one watering method to the other.

If you overseed the lawn, or reseed bare spots, still water frequently and shallowly until new grass is 2-3" tall.

In your area, I further more recommend that you fertilize in late spring, early fall and late fall (may/sept/nov). Do not fertilize during hot summer months.

Good Luck
Kenneth