Much like some animals, most types of lawn grasses “hibernate” during winter, when their growth drastically slows during cold temperatures. Although cool-season grasses (tall fescue, bluegrass and ryegrass) remain green, most warm-season grasses (bermudagrass, zoysiagrass, St. Augustinegrass and centipedegrass) typically start to discolor and turn tan after average temperatures drop under about 50°F and particularly after the first hard frost of late fall. This is the way the grasses protect themselves from bitter, sub-freezing temperatures.
However, in most cases (unless your area experiences prolonged periods of very cold temperatures), lawn grasses remain alive during their long winter’s nap. They then resume growth when warm, sunny spring weather returns (just like trees that regrow their leaves in spring).
Mowing is typically not necessary in winter, but it’s important not to let fallen leaves remain on the surface of the lawn. Doing so can smother the grass plants, create conditions favorable for turfgrass diseases and possibly invite insects and voles to burrow underneath.
Even though the grass on top may be dormant now, grass roots still continue to grow (although slowly) throughout winter unless the soil is frozen. That’s why it’s important to continue to irrigate your lawn, especially during dry, warmish and windy periods. Desiccation (extreme drying of the grass in winter) can lead to winterkill and necessitate the replacement of dead grass in spring. We’ll discuss winterkill in more detail in a future blog post this winter.
Greening up your dormant warm-season lawn
Some homeowners of warm-season lawns actually like the look of winter dormancy, which can create the image of a tawny-tan carpet surrounding their home. And, after weekends spent fertilizing and mowing during the growing season, they also like the low-maintenance aspect of a dormant lawn. Others, though, prefer a lawn that’s green all year long, so they have a couple of options — either overseeding in late summer or early fall with a temporary annual ryegrass (which will die out the next summer) or “painting” their lawns with a turf colorant.
Overseeding with ryegrass in fall does provide a beautiful green lawn in winter. However, it continues to need mowing during growth spurts (in warmish weather), and it requires fertilization later in fall than warm-season grasses do.
To “paint” your lawn instead, a quick online search for “grass colorant” will give you several product options (although the “green” colors may vary widely among different products). Most turfgrass researchers feel that a turf colorant is better, in the long run, for dormant warm-season grasses than overseeding. Unless removed with a selective herbicide in spring, ryegrass can sometimes persist into early summer, competing for sunlight, water and nutrients with the warm-season grass as it’s coming out of dormancy. If you choose to use a turf colorant, check first to make sure it’s safe for your lawn grass (most products are), and then read and follow the instructions carefully.