Q: What is over-seeding? Why is it important to lawn care? When and with what?

Jeannette Cross answers your questions about over-seeding, why it’s important, and when and how to go about properly over-seeding your lawn in her Ask an Expert series.

A: Over-seeding is applying a suitable blend of grass seeds to an existing lawn to replenish grass cover to create thick grass that will crowd out weeds.

overseeding lawn services and tipsIn the spring one should check for dying grass and repair it with over-seeding and top dressing. Weed seeds are very opportunistic and will establish themselves wherever bare soil exists.

Top dressing is the addition of organic material such as compost to the surface of the soil or lawn to improve soil structure and nutrients. Over-seeding (sowing seeds on an established lawn) is one way to ensure your lawn stays dense from one season to the next. It is not necessary to cover grass seeds with soil unless there are bare areas which then need top dressing too.

Over-seeding is done with a broadcast spreader to evenly apply the grass seeds. The lawn needs to be kept moist until the seeds germinate which takes between 8 and 15 days dependent on the weather and type of grass seed. The morning dews in the spring and fall are conducive to grass seed germination from over-seeding. Spring over-seeding is essential for repairing areas where the grass has died or is thin after the winter and is best done between the end of April and the end of May.

Over-seeding in the fall is extremely important and beneficial because: in the fall there is less competition from annual weeds; young seedlings can tolerate the winter cold but can easily die off in the heat of summer; the ground is warm and the air is cool which is ideal for germination; and fall rains tend to be gentler.

Over-seeding is also done with a blend of grasses as variety in your lawn creates a healthier and more naturally resistant lawn. Certain diseases and insects favour certain types of grass.

A mixture of grass types will mean that your lawn will be better prepared to recover from any injury; adapt to the varying levels of light from the sunny spots to the shady areas of your lawn; and better able to resist insects.

Kentucky bluegrass grows well in sunny areas.

Fescues are good for partially shady and dry conditions. Perennial ryegrass grows quickly, is drought tolerant and pest resistant. Many fescues and ryegrasses are infected with a naturally occurring fungus called endophytes.

Grasses that contain these fungi have shown high resistance to insects such as billbugs, chinch bugs and sod webworms that feed on the blades of grass. These grasses are more vigorous with a greater number of roots making them more drought resistant too.

In Canada the grass species that are grown are called cool season grasses. This means they do most of their growing during the times of cooler temperatures in the spring and fall. Cool season grasses tend to go dormant during the heat of summer and start growing again with the fall rains. Species of cool season grasses include Kentucky bluegrass, perennial ryegrass, fine fescue and tall fescue.

Have a question? Please comment below!

For over-seeding, top dressing with over-seeding and/or a complete lawn care program contact harmonygardens@sympatico.ca.