With cooler fall weather and little measurable rainfall the past several weeks, the growth rate of lawn grasses has slowed considerably in Greater Columbus, and most homeowners have been happy to leave the lawnmower in the garage.
As the weather gets cooler and the amount of daylight gets shorter, the need for lawn maintenance tasks slows down and typically comes to an end when the ground freezes. But the cool weather and shorter days of late fall don’t signal the end of the need for certain lawn maintenance tasks. In fact, late fall is one of the best times of the year to improve a stand of lawn grass, when an investment of time, sweat, and some lawn care inputs will yield a healthier, greener, and thicker stand of turf earlier next spring.
Fall is the time when cool-season grasses recover from summer stresses such as drought, heat, and disease and is also the time when turf grasses begin to store carbohydrate reserves in the stems and rhizomes. These carbohydrate reserves help grass plants fight winter injury and disease and, more important, serve as a source of energy for root and shoot growth the following spring.
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Late fall fertilization will provide better winter color of the stand, quicker green-up in the early spring, and an increase in root growth. Late fall applications of fertilizer are more important to the health of lawn grasses than spring fertilizer applications more commonly practiced by most gardeners.
Timing fall fertilizer applications
The best time to make late fall applications of lawn fertilizer is around Thanksgiving or the very beginning of December, when the grass stops actively growing or has slowed down to the point of not needing to be mowed. Even though the leaves and shoots of the grass plant have dramatically reduced their growth rate at this point, the roots are still actively growing, allowing the plant to make maximum use of available fertilizer in the soil. It is common to apply fertilizer following the last mowing of the season, but fertilizer applications should never be made once the ground is frozen.
Choosing a fertilizer blend
Most cool-season lawn grasses require 2 to 4 pounds of nitrogen (N) per 1,000 square feet each year, and a majority of this nitrogen should be applied in two fall applications: one in September and the other in November. If you missed the September application window, don’t fret, just proceed with a single application this month.
A complete fertilizer with a high ratio of both nitrogen (N) and potassium (K) is essential for root growth, winter hardiness, and disease resistance. An ideal fall fertilizer blend will have a nitrogen to phosphorous to potassium (N-P-K) ratio of 24-4-12.
When shopping for lawn fertilizer, you may find that some fertilizer manufacturers have completely removed phosphorous (P) from some fertilizers in Ohio due to overuse and the environmental harm caused when excess phosphorous is carried into surface waters such as streams and lakes. If you are unable to purchase a complete lawn fertilizer that contains nitrogen, phosphorus, and potassium, choose one with only nitrogen and potassium as these two nutrients are most needed by grass plants at this time of year.
Fall lawn weed control
November is also an excellent time to control many annual weeds in the lawn. Populations of winter annual weeds such as purple deadnettle, hairy bittercress, henbit and common chickweed all seem to have exploded in greater Columbus the past few years. These cool-season weeds are in the small seedling stage right now in Greater Columbus and treating them with an herbicide at this growth stage can be an effective method for removing them from the stand in advance of green-up next spring. Other annual weeds such as dandelion, plantain and even clover can also be controlled in late fall when these plants are still actively growing.
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Applications of lawn herbicides are best done when the daytime temperatures are 50 degrees degrees Fahrenheit or greater, so be sure to keep an eye on the weather forecast when planning an application this month. Always use the ester forms of lawn herbicides in the fall as these formulations are more effective than amine forms in cooler weather.
So slip on your warmest hoodie, find that fertilizer spreader in the back of your garden shed and provide some nutrition for your lawn at the time of year when it is most needed — late fall and early winter.
Mike Hogan is an associate professor at Ohio State University and an educator at the OSU Extension.