1.Cease lawn mowing when temperatures are cool to cold and the grass shoot growth has essentially stopped. Reducing mowing heights to 2.0 - 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 is 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. Photo 1 (left). Lawn mowing should continue through the fall. Bob Mugaas.
2. A thin layer of leaves can be left on the lawn as long as they are ultimately chopped up as the lawn is mowed through the fall.
3. When confronted with several inches of leaves over the lawn, it is best to rake off the majority of those leaves before mowing and either compost them 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. Photo 2 (left): Acceptable leaf cover that can be ground up adequately with a lawn mower. Bob Mugaas.
4. Early October can still be an excellent time for controlling those pesky perennial broadleaf weeds such as dandelion and creeping Charlie. Best control with most available herbicide products is achieved when daytime temperatures are above 50o F. but less than about 80o F. That's usually not a problem at this time of year. 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. Photo 3 (below and right). Young and mature dandelion plants are best controlled in the fall. Bob Mugaas.
5. 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.
6. As a general rule-of-thumb, it is 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. A fertilizer application about the time of the State Fair provides the additional nutrients for the fall growth period, while the late season application is primarily stored for growth next spring. It is often easy to tell which lawn has had a late season application of nitrogen as they will usually be noticed as the first lawns with healthy growth and a dark green color in early spring. Photo 5 (above and left): Photo taken in early May. Dark green strip received a late season N application the fall before; surrounding turfgrass area did not. Bob Mugaas7. With the current dry period we are experiencing, 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 as during the summer months, applying that same amount during the fall may be sufficient for two or perhaps even three weeks depending on weather.
With a little effort and planning this fall, successfully preparing the lawn will help it survive the upcoming winter months, while also encouraging a healthy start for next spring. It may seem a little backwards, but preparation of a healthy spring lawn begins the previous fall. For additional information on any of the topics mentioned in this newsletter, please see the lawn care section in our Sustainable Urban Landscape Information Series website at www.sustland.umn.edu.