By Sam Bauer
Q: What mowing height should I keep my lawn at before winter?
A: Generally we suggest to keep your lawn at the same height as you’ve had in the fall. Cutting the lawn short prior to winter has been commonly suggested in the past as a means of reducing spring damage from snow molds and voles, but cutting the lawn too short will be more of a stress to the grass than the injury you may experience from diseases or critters. If the standard mowing height for your lawn is 2.5 to 3 inches, we suggest to keep it at that. If the height is 3+ inches, then we would recommending bringing it down to 3 inches before winter. If you do plan to lower the mowing height, be sure to mow several times at this height, not just the final mow. The goal is to condition the grass to this new height with several mowings prior to winter. Again, we may only suggest this if you have had snow mold issues in the past of if you maintain your grass at a long height in the fall. Also, be sure to continue mowing until the grass stops growing, this will help reduce snow molds and winter damage. You can use a bagging attachment on the last mow of the year to help remove any excess organic matter and leaf litter.
Q: Should leaves be raked off of the lawn or mulched with a mower?
A: It depends. For homeowners with numerous trees, it may be impractical to mulch all of them into the lawn without smothering the grass at some point. In that case we would suggest mulching a majority of the leaves into the lawn and raking up the rest. Be sure you can see at least 80-90% grass after mulching leaves, this will ensure that the leaves aren’t smothering the grass. To practically mulch all of your tree leaves, you may need to be out with a mower more often than your grass needs to be cut, because if too many leaves fall you may not be able to mulch them into the the lawn.
Tree leaves contain organic matter and many nutrients that can be beneficial to your lawn. For example, a study conducted in New Jersey on 100 municipal trees demonstrates nutrient content of 1% nitrogen, 0.1% phosphorus, 0.38% potassium, also secondary macro nutrients and micronutrients (1). The organic matter will also benefit the lawn my increasing moisture holding capacity and improving aeration. Standard mowers will work, and we suggest to close the side discharge for mowers that have one. Closing the side discharge will contain leaves in the mower so they get chopped up better before they fall into the grass canopy. Mulching blades can be purchased as well.
Here are some resources that help to further explain leaf mulching:
WCCO Good Question: Do we really need to rake?
Minnpost: Leaf bagging under scrutiny as a wasteful expense and pointless chore
Q: Is it too late to fertilize my lawn?
A: Yes. New research on late-fall fertilization demonstrates that a majority of the fertilizer applied in late-fall (late-October or early-November) can be lost to the environment because lawn grasses are not able to absorb fertilizer as well when temperatures are low. For Twin Cities residents, we suggest to not apply fertilizer past mid-October. Here is more information on this research and our recommendations: Apply lawn fertilizer by mid-October
Upper Midwest Lawn Care Calendar for Cool Season Grasses
Q: What is dormant seeding and when should that be conducted?
A: Dormant seeding is a practice that involves seeding when temperatures are too low for the seed to germinate prior to winter, and it is expected that the seed will germinate in the spring. This can give you a jump on spring seeding. Germination prior to winter is bad and seedlings will generally die if they haven’t matured. Sometimes it is a bit of a waiting game at this time of year. The trick is to find the time when soils are unfrozen so that seed can be worked in slightly, yet air temperatures must be cold enough so the seed won’t germinate. Wait for high daytime temperatures of 35-40 degrees before seeding.
Q: Is there an advantage to dormant seeding versus spring seeding?
A: Yes and no. A dormant seeded lawn could mature as much as one month faster in the spring than a spring seeded lawn. This is because some of the germination process actually starts prior to winter in a dormant seeded situation, although the shoots still haven’t emerged from the seed. When temperatures are adequate in the spring, complete germination occurs. In this case the seed actually dictates when temperatures are warm enough to grow. Just like late-fall, temperatures and weather patterns can be unpredictable in the spring. For this reason, the best timing for spring seeding is difficult to predict, which can delay the timing to actually sow seed. Still, there some negative aspects of dormant seeding to consider. First, because of the spring temperature fluctuations, it is possible to have good seedling establishment initially, but a cold spell during this time will injure these seedlings. Also, there is a greater potential for seed loss over the winter due to erosion and water movement, predation, and decay. These positive and negative aspects should always be considered during this process. Here is more information on dormant seeding lawns:
Dormant Seeding Lawns: Last chore of the season