As summer begins to wind down, your mind may already be on snow removal or Christmas light installation services, but there is another important service you need to be offering clients at this time: winterizers.
This application of fertilizer in the fall is key for both warm-season and cool-season grasses, though for different reasons. Warm-season grasses such as bermuda grass, St. Augustine grass, and zoysia grass benefit from a fall feeding because they are coming out of their growth season and need to prepare for winter.
Potassium is the key ingredient needed by warm-season grasses in the fall, as this is the element that promotes winter hardiness. They can handle low amounts of nitrogen, but not too much, since that element promotes more plant growth.
“For warm-season turf species, don’t apply nitrogen any later than four to six weeks before the first killing frost,” said Eric Miltner, an agronomist for Koch Turf & Ornamental. “If there’s too much nitrogen, it will lead to less winter hardiness, and it makes them more succulent and susceptible to damage. Cool-season species can be fertilized later into the fall while growth continues.”
Cool-season grasses reap multiple benefits from winterization fertilizer. Fescues, bluegrass and ryegrass are examples of the types of grass that are coming out of summer suffering from heat stress and drought stress. Applying nitrogen ensures these types of turf have the nutrition needed to repair and grow.
“You ask any turf expert for lawn care tips and they are going to tell you the key to a strong lawn is strong roots, and the key to strong roots is to give your cool-season grass lawn two feedings in the fall,” said Ashton Ritchie, a lawn and garden expert with Scotts Miracle-Gro. “Warm-season grass lawns benefit from a single September feeding.”
According to Miltner, there are three main goals you can accomplish with a fall application of fertilizer for cool-season grasses, and the timing of the application will vary based on which goal you are trying to achieve.
Summer recovery can be accomplished by applying in September while extending color into the winter can be attained by spreading during October and November, depending on the location and the weather. Winter hardiness can also be achieved by an application during the fall.
“The thing you need to keep in mind is, as the temperatures cool down, the grass can still take up the nutrients, but it takes them up at a much slower rate,” Miltner said. “The later it is, the longer it takes to absorb the nutrients.”
Ritchie advises feeding cool-season grasses twice in the fall because the second application – six weeks after the first – helps lock in what you’ve gained.
“What’ll happen is that your lawn’s increased root mass will absorb and store the nutrients from the fertilizer,” he said. “Once spring arrives, your lawn will quickly tap into these nutrients for a beautiful burst of green. In fact, a lawn fed twice in the fall will stay green longer into winter and be the first to green up in the spring.”
When it comes to what form of fertilizer to use, it all comes back to your objective.
“Something like a sulfur-coated type product is good to use earlier in the fall,” Miltner said. “Slow-release fertilizer provides a good amount of nitrogen over time. A polymer-coated product will release nutrients in the fall, then shut down in the winter. It allows flexibility so you can apply later and get extended nutrients. It may cost more, but you get many months of nutrition.”
According to Ritchie, slow-release or controlled-release lawn food that spreads the nutrition out over a span of six to eight weeks is better than doing a one-time “dump” of nutrients that only generates a surge of top growth.
It is also better to use granular fertilizer later in the fall so the unused nitrogen isn’t lost to the environment.
“You need to know what you’re trying to achieve and match that objective with the best fertilizer and think about the environmental impact,” Miltner said.