How to lessen frost’s grip on your plantings
The cooler days of fall are settling in — there was a light frost present on some lawn areas in mid-October at the Garden. I just checked the long-range forecast and did not see any freezing weather coming in the next couple of weeks, but eventually there will be cold nights with heavy frost.
It’s best to stay off the lawn when there is frost present. Frost on the grass indicates that water inside the leaves is frozen so traffic on the turf can cause the frozen water in the cells to rupture, which can kill or severely stunt the leaves. Grass 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 leaves. 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. The tomatoes in my garden at home were finished so I removed them before frost hit them. 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 on my lawn to save time on raking them.
My mowing schedule now is driven more by leaf cover than the height of the lawn. I have dropped my mower height to two and a half inches. If you have a lot of trees in your garden, you may need to remove some leaves to avoid smothering the lawn with the shredded leaves.
The dry weather has dramatically slowed the growth of turf this fall, and cold weather will eventually stop the grass growth. Make your last cut of the year at a height of two inches.
• Tim Johnson is director of horticulture at Chicago Botanic Garden, chicagobotanic.org.