Using Growth Tarps on Sports Fields
Growth tarps have several uses on sports fields. They help protect turfgrass from frost, extend the growing season in the fall, and encourage green-up in the spring.
Sports field managers in different geographies use growth tarps differently. However, there are some general best practices. Growth tarps work by trapping heat in a greenhouse microclimate. They’re made of semi-permeable material that allows sunlight to penetrate. Depending on how dark the blanket is, it may absorb more heat. Generally, though, growth tarps serve to insulate heat, not to generate heat.
Because tarps are semi-permeable, the grass and soil underneath still receive the moisture and air circulation they need. The soil under the blanket cools more slowly than the surrounding air. Elevated soil temperatures delay turfgrass dormancy and provide extended root, shoot, and leaf growth during cold weather.
To promote an effective microclimate under a growth tarp, make sure the edges of the blanket extend well beyond the edges of the area you want to cover. Some managers only place tarps on select, high-traffic areas that need the most help with recovery. Regardless of the size of the tarp, it’s important to secure it well. Whether you use stakes, nails, or staples, choose something with high visibility so you won’t accidentally hit them with a mower. You could even use non-metal stakes to eliminate the risk of a dangerous, expensive accident. Finally, you’ll want to air out the tarps and give them time to dry before storing them for the season.
Read on for more geography-specific recommendations.
In northern climates, growth tarps are most commonly used to speed turfgrass recovery on soccer and football fields during cold weather. They’re also used to “warm up” turfgrass in the spring and kickstart growth before the season starts.
With most sports fields in the North being ryegrass or Kentucky bluegrass, temperature is a good indicator of when to apply a growth blanket. Once nighttime temperatures reach the 30s or low 40s, you can use a tarp to help extend the growing season. If daytime temperatures exceed 55°F, you would want to remove the tarp during warm hours to minimize the risk of fungal growth.
It’s a good idea to make a preventative fungicide application a day or two before covering the field with a growth blanket. You can apply a PGR at the same time if traffic on the field is light, but not if traffic is still consistent. If the area you’re covering has been overseeded, you can also make a light foliar fertilizer application to encourage germination.
In the transition zone, sports fields can be cool-season, warm-season, or a combination of the two types of grass. Bermudagrass is commonly overseeded with ryegrass in the fall, which creates unique demands for growth tarps in the transition zone. Tarps are most commonly used on professional and college fields with larger budgets and staff.
When it comes to delaying dormancy in the transition zone, growth tarps are especially helpful for warm-season grass because it goes dormant earlier than cool-season as temperatures fall. The appropriate time to apply a blanket on warm-season grass in the fall depends on temperature and scheduling needs for the field. Generally, temperatures below 50°F indicate a good time to cover the field. You can still remove the tarp during warmer daytime temperatures to allow the field to absorb heat, then cover it again to maintain that warmth overnight.
For cool-season grass in the transition zone, growth blankets help protect from frost in the fall. They also help promote seed germination. And as you prepare for spring sports, you can use growth tarps to encourage an earlier green-up, which is especially effective for cool-season grass because it naturally comes out of dormancy at a lower temperature than warm-season.
When using a blanket to help with spring green-up, it’s best to apply the tarp in the late fall or early winter before the ground freezes. That way, it’s easier to stake down. Then remove the blanket a week or so before the start of the spring season, so the field has time to dry and get a fresh mow. You can use the same method for warm-season grass, but keep in mind that it will need warmer temperatures to come out of dormancy in the spring.
In warmer parts of the transition zone, you can use growth blankets to keep bermudagrass from going completely dormant over the winter. Bermudagrass will stay semi-dormant under a tarp if it’s covered before the first frost. Then it can come out of semi-dormancy more quickly than it would come out of complete dormancy. After spring green-up, though, it’s crucial to cover the field back up for any frosts in the late spring. With dramatic daily temperature swings in both fall and spring, it’s helpful to uncover turf during the warmest hours of the day and cover it back up for colder conditions.
In addition to growth blankets, turf paint helps encourage spring green-up on your field. By creating a darker canvas, turf paints like Sempre Verde allow the grass to absorb more heat and come out of dormancy more quickly. You can paint dormant or semi-dormant bermudagrass and still cover it in cold conditions to maximize spring green-up.
It’s also important to remember that growth tarps don’t solve everything. Grass still needs water to grow and green up. It also needs time to restore its energy, which is why it naturally goes into dormancy. You can limit dormancy to maximize growth, but you can also maximize growth by allowing grass to go dormant for a time. Your ATS representative can help you find the balance between the two.
Special thanks to Kevin Breuker, Greg Hogan, and Chris Fondren for contributing to this blog post.