Every Monday we tackle common lawn and garden questions on Home Dish. Today we referred to expert Bob Mugaas, turfgrass specialist and horticulturist and program director of the U of M Research and Outreach Center. For more information about Master Gardening programs in your county, visit extension.umn.edu/master-gardener.
Now that it’s October, we have to treat our lawns a little differently. Stop mowing your lawn when temperatures are cool to cold and the grass shoot growth has essentially ceased. Reducing mowing heights to between 2 and 2.5 inches for the last two or three lawn mowings of the season will reduce the amount of leaf tissue present over winter, and can reduce the amount of snow mold that may occur. It’s not necessary to collect clippings as long as they can filter down into the turfgrass canopy at the soil surface. Excessive amounts of grass clippings should not be left on the lawn surface in the fall or at any other time of the year.
You can leave a thin layer of leaves on the lawn, as long as they are ultimately chopped up as the lawn is mowed throughout the fall.
When confronted with several inches of leaves over the top of your lawn, it’s best to rake off the majority of those leaves before mowing. Either compost those leaves or use them as mulch material in other parts of the landscape. A thick layer of leaves left on the lawn blocks out sunlight to the grass and may even smother the existing grass beneath that layer, resulting in large areas of thin or even dead grass come next spring.
Early October can still be an excellent time for controlling those pesky perennial broadleaf weeds such as dandelion and creeping Charlie. Be sure that neither the grass nor the weeds you are intending to treat are under any drought stress. Drought stress will usually result in less than satisfactory control and may even injure the desirable lawn grasses because they can become susceptible to broadleaf herbicide injury under such circumstances. Always follow product label directions for proper use whether in the fall or any other time of the year.
In the Twin Cities, a late season application of nitrogen fertilizer should be put down around Halloween. At this time of year, the nitrogen is taken up into the plant and stored in the crowns, rhizomes, tillers and/or stolons where it can be quickly accessed next spring by the growing grass plant. Follow this application with about ¼ to ½ inch of water to move the nutrients into the soil, where they can be taken up by the roots. Never apply fertilizer to frozen ground. You would like about two to three weeks of unfrozen ground following this fertilizer application to allow for root uptake of the nutrients.
As a general rule-of-thumb, it’s best to avoid stimulating excessive shoot growth during late September to mid-October. Succulent growth associated with higher nitrogen levels can contribute to increased incidence of snow mold over winter.
Regular watering should be continued throughout the fall period or until more frequent rainfall returns. While you may not need the one inch of water per week like during the summer months, applying that same amount during the fall may be sufficient for two or even three weeks, depending on weather. Late summer and fall are a naturally active growth period for our lawn grasses. Making sure they have ample water and nutrients during that time will aid their recovery from summer stresses and encourage healthy growth for the next growing season.
Any reseeding of the lawn should have been completed by mid-September in the Twin Cities area. Avoid seeding during early to mid-October, as the very young seedlings that do emerge often have poor survival over the winter. If you would still like to do some seeding, you can do what’s known as dormant seeding. Before the ground is frozen, but while the soil is cold (so as to not encourage seed germination in the fall), incorporate the seed into the soil surface. Incorporating the seed into the soil surface will help protect it through winter. The seeds remaining in that ‘dormant’ condition until next spring can get a headstart on germination and growth for the next growing season. In the Twin Cities area, dormant seeding is usually done in early to mid-November, depending on weather conditions.
With a little effort and planning this fall, successfully preparing the lawn will help it survive the upcoming winter months, while encouraging a healthy start for next spring. It may seem a little backwards, but preparation of a healthy spring lawn begins the previous fall!