Why Can’t Cool Season Grass be Planted in Summer?

Why Can’t Cool Season Grass be Planted in Summer?

Valley Green has been an expert in turf and grass seed for over thirty years. Our custom grass seed blends are some of our best-selling products. Our busiest time is usually in spring or late fall because that is a very popular time to seed lawns with cool season grasses. We have heard the question recently of why can’t cool season grass be planted in summer? From the heat to weeds, there are many reasons cool season grasses like Kentucky Bluegrass, Perennial Ryegrass, and Fescues should never be planted in summer.

Why Can’t Cool Season Grass be Planted in Summer?

Cool season grasses will likely go dormant if planted in summer.
When soil temperatures go above 65 degrees, most cool season grasses will grow dormant. This means growing is impossible. Since it is common in summer for soil temperatures to reach that level, it is not recommended to do any sort of planting. Trying to plant seed in high summer temperatures can result in low seed germination and seedling death.

Cool season grass planted in summer face competition from weeds.
Any homeowner or landscaper knows that weeds are an ongoing battle throughout the summer. If you try to plant cool season grasses, they will already be under stress from the heat. Weeds will make the growing conditions worse because the seedlings will have to fight for nutrients with them. By late summer, annual weeds will have completed their life cycle which will allow newly planted grass seed to flourish and grow without competition.

Grass planted in summer is susceptible to turf disease.
With the current wet and warm conditions in the northeast, the potential for a breakout of turfgrass disease is very likely. Grass that is just starting to grow is unlikely to survive any of these diseases. Pythium Blight and Brown Spot frequently show up in warm and wet weather. They also have a tendency to spread quickly so you may not notice the disease on the new grass until it has taken hold.

Grass planted in summer can get eaten by birds and insects.
Grubs love to eat the roots of newly planted grass and they are most common in late summer. If you attempt to plant grass seed at the end of July or in early August, your seedlings may not get a chance to grow before their roots are eaten. Wild birds also love to eat newly spread seed. In the northeast, the populations of wild birds are higher in summer because they have not flow south for the winter. Choosing to spread seed in early fall when they have departed for the south will ensure the seed does not end up getting eaten.

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