Overseeding is the practice of adding new grass seed to your lawn so that is grows more thickly. Overseeding is also done to replace the grass type you have - usually to a more hardy grass that needs less water or fertilizer. Click here for more on hardy grass types for Calgary and where to get grass seed.

When to Overseed

Overseeding is most effective when done in the Spring or in the Fall when the weather is not hot and the tender grass seedlings will do well. If you overseed in May, June or September you will have to water daily for about 10 minutes (when it does not rain) to keep the seedlings moist so they will sprout.

Overseeding in late Fall is the easiest way to overseed. You need not water - just let the winter snows melt and encourage the seeds to sprout. With late Fall overseeding, you won’t get quite as many seeds germinating as in Spring or early Fall.

It Usually Takes 2 - 4 Years for New Grass Types to Take Over

Generally you need to overseed once a year for 2 - 4 years for the hardier grass type to take over your lawn. Your grass will be thicker and greener during the process. If you want hardier grass types to establish sooner with overseeding, stop watering your lawn once the new seeds have sprouted and are a couple of inches high. The hardier grass types will then compete better with grass types that are probably in your lawn now (e.g. Kentucky Bluegrass). If you’re in a hurry, you could overseed in the Spring and then again in the Fall.

Spread a Thin Layer of Compost to Overseed

Spread a 1 cm. or 1/4 inch layer of compost over your lawn first. Click here for spreading compost information.

Then use a seeder to spread the grass seed. A drop seeder will spread the seeds more accurately than a broadcast seeder. Spread half the seed you need in one direction back and forth over your lawn. Then spread the other half of your seed over your lawn by going back and forth in the other direction. Use the amount of grass seed recommended by the supplier.

Avoid using corn gluten for a month before overseeding. It will stop the seeds from sprouting.

Click here for actions you can take to support a pesticide bylaw.