Frost signals time to be cautious with certain plants

It is best to stay off the lawn when there is frost present.

Frost on grass indicates that water inside the blades is frozen, and traffic on the turf can rupture the frozen cells, which can kill or severely stunt the blades.

The symptoms will generally appear purplish to black in color at first and then progress to a straw color. When frost is very heavy, the cell disruption can occur at the crown and kill the entire plant. If there is no damage to the crowns, the turf will recover from the generation of new blades.

Once the ground is frozen, there is less of an issue as everything is solid, so the cells can't rupture.

• After a killing frost, remove dead plant debris from annual and vegetable beds.

Sanitation is especially important if you have had disease problems in your planting beds. Remove all diseased foliage, vegetables or fruits, and do not add this plant debris to your compost pile.

Most home compost piles do not get hot enough to kill disease organisms and you could possibly introduce disease organisms back into the garden when you use the compost.

• Continue cutting your grass throughout the fall as needed, taking care to stay off the lawn when there is heavy frost present. I like to use a mulching mower to grind up the leaves that fall on my lawn to save time on raking them.

You may need to remove some leaves if you have a lot of trees in your garden in order to avoid smothering the lawn with the shredded leaves. Cold weather will eventually stop grass growth. Make your last cut of the year at a lower height of 2 inches.

• Tim Johnson is director of horticulture at Chicago Botanic Garden, chicagobotanic.org.