Keeping grass green during frosty weather

The fall season’s cleanup is nearly complete, with a lion’s share of the autumn leaves raked and discarded, but there are a few other lawn-cleaning issues to consider when maintaining green grass throughout the winter.

While grass may not appear to be growing during the winter months, Vince Marrocco, the chief horticulturalist at Morris Arboretum, says it most definitely is, only at a slower rate than during warm-weather months.

He says most lawns in the region have what is known as “cool season turf grass,” which includes fescue, ryegrass, and bluegrass that stay green year-round.

With the cold temperatures of late fall and early winter, grass blades coated with frost may look picturesque, but Marrocco advises that if people want their grass to remain green after it thaws, they should avoid walking or driving on it. The pressure from feet or a car’s tires can damage the grass.

Frozen grass blades have ice crystals between the leaf cells, which protect the cells from damage. Marrocco says driving a car or walking on frosty or frozen grass pushes the ice crystals into the cells within the leaf and causes them to pierce the cell walls. 

“In essence, the frozen and frosted grass leaf blade is poked to death by thousands of sharp daggers, creating countless holes inside and out,” he says. Damaged grass blades will turn that section of the lawn brown and unsightly.

“If you’re at the Arboretum when we’ve had heavy frost, we tell everybody to stay off the grass,” says Marrocco. “Although you won’t kill it walking on it, you’ll disfigure it. It won’t look as pretty.”

To maintain the Arboretum’s 92 acres of lush gardens, the garden’s staff follows standard guidelines, fertilizing only in the spring and fall. Marrocco advises against fertilizing in the winter months.  

“Turf roots grow slowly and absorb nutrients slowly, and, therefore, only need a little bit of fertilizer,” he says. “Chances are that if you fertilize in the winter, most of your fertilizer [and] money will either run off with the rain, or leach straight through the soil past the roots and into the ground water.”

Grass 145