Lawn fertilization needs vary by region
Q: We moved from California to Wisconsin back in June. One of my neighbors said that he fertilizes his lawn in November. I know there is a difference between my old warm-season lawn and a cool-season lawn, but November, really? What do you think?
A: You are right; there is a big difference in the lawn grasses from the warm south to the cool north. If you think about it, fall, winter and spring are three cool seasons in a row. If you are going to only fertilize a cool-season lawn once a year, then do it in September, as the lawn begins the three cool seasons. If you are going to only do it twice, then September and November are the best times. If you fertilize three times, then add May. Finally, if you have a lawn that will be actively used and irrigated, then do a half-rate fertilization in June. In other words, don’t follow a program that applies a bunch of fertilizer in the early spring and during the summer.
Why do a November fertilization? The top of the plant will be slowing its growth, but it will still produce carbohydrates during photosynthesis. Instead of growing longer leaves, the food helps the plant through the winter and is used in the spring to green up early. The plant will also grow more roots in the spring. Fertilizer applied in March and April will produce more leaves that will just be mowed off. The fast early-spring growth of leaves also tends to get more diseases that show up in the summer.
The extension offices of research universities across the country regularly state that lawn fertilizer may not need any phosphorous or may only need it when a soil test shows a need. Potassium should also be very low unless a soil test shows a need. The recommendation for nitrogen is usually a maximum of 4 pounds per 1,000 square feet per year and no more than 1 pound per 1,000 square feet during any application. It is often best that at least 70 percent of the nitrogen be in slowrelease forms. Leaving lawn clippings on the lawn after every mowing can equal ½ pound of nitrogen per fertilizer application. The exception to this is that the November fertilization can have a more fast-acting nitrogen like urea or ammonium sulfate. Q: How thick of a layer of chopped-up leaves can I leave on my lawn? I have a mulching mower, but I don’t know how much I can leave on the grass. A: You can mulch tree leaves on the lawn over and over again in the fall as long as you can still see a lot of the grass leaves sticking up through the mulched leaves. The grass plants need to produce carbohydrates for as long as possible to help them survive the winter.
Once you have reached ½ to 1 inch of mulch on the lawn, you can start saving the mulched leaves and applying them to flower beds. A 2- to 3-inch layer is good in the beds. If you have more and you have a vegetable garden, then apply several inches to the top of the soil and rototill it in. If you still have more, then mix them into a compost pile.
Only bag them up to put on the curb if you have no other option. Why pay to dispose of organic matter only to turn around in the spring and buy compost for the garden?
Email questions to Jeff Rugg at info@greenerview.com.