In the north and transition zones, it is not uncommon for a lawn to be covered in frost on a cold fall morning. Whatever you do, stay off of it!
What Causes Frost?
Frost occurs on cold, clear nights when atmospheric conditions cause objects, like grass, to become colder than the surrounding air. Depending on the conditions, frost can be light and scattered, or heavy enough to kill flowers and bring on dormancy in plants.
Why Stay Off It?
When a lawn is frosted, the grass blades are literally frozen. Any activity on the lawn while it is frosty, like walking on it or mowing it, will "break" the grass blade and damage the lawn. It will recover eventually, but it may not fully bounce back until the following spring.
On a frosty morning at a golf course, nobody moves until the superintendent determines the course frost free. The frost dissipates as the sun rises and the air warms up. Sprinklers are sometimes turned on for thirty seconds or so to speed up the process, especially in the shade.
For a homeowner, deliveries, mail-persons, or children are usually responsible for unwittingly damaging the lawn.
