October 30, 2015
Fall Lawn Care
The lawn care season is winding down, but has not ended. Several important lawn care tasks for the next couple of weeks should include a final fertilization, continued mowing as needed, removing leaves that have fallen, and draining the irrigation system after watering in the last fertilizer application if Mother Nature doesn’t do that for us.
The last fertilization of the season is recommended to be about the time of the last mowing, usually in late October or the first week of November. It is an important application for promoting root and rhizome growth in still warm soils, and for spring green-up to help avoid applying fertilizer early in spring when soil temperatures are too cold.
A myth about the last fertilization is that fertilizer high in phosphorous and potassium is needed. This is not the case. With few exceptions, our soils have adequate levels of phosphorous and potassium. With this application, nitrogen is still the nutrient most needed.
When buying winterizer fertilizer, many of the products have high percentages of phosphorous and potassium. The analysis on the bag is a number such as 8-12-20. A fertilizer with this analysis has 8 percent nitrogen, 12 percent phosphorous and 20 percent potassium. A fertilizer with an analysis such as 25-5-5 would be better to use. At this time of year we want a rapid release form of nitrogen such as urea or ammonium sulfate.
All applications of lawn fertilizer need to be watered in. This moves nitrogen into the soil for roots to take up and decreases the risk of fertilizer running off lawns during heavier rain storms or along with snow melt. During winter, when soils are frozen, snow melt runs off lawns and you can lose the fertilizer you applied earlier.
Rake or mow tree leaves on a regular basis to avoid the build-up of leaves on a lawn for longer than 3 to 4 days. If leaves remain on the lawn after mowing, mow again when leaves are dry. Pulverize leaves by using a mulching mower or making two or three passes. After mowing, the pulverized leaves should not cover the turf, but filter into the grass.
When mowing the lawn in late fall, it is not necessary to lower the height. We used to suggest lowering the mowing height in the fall. But more recent research has shown it is more beneficial to the turf to keep the mowing height the same, about three inches, all year. This will maximize rooting and increase the stress tolerance of your turf.
Unless the weather patterns change, one thing that will be particularly important this fall will be to water turf, perennials, shrubs and trees. Turf and perennial flower beds should be watered until the soil is moist to a depth of six to 12 inches. Depending on your soil texture and how dry the soil is now, this might take one to two inches of water.
Trees and shrubs will require more water. I water my shrubs by laying a hose near the base of the shrubs and letting it run at a moderate rate for about 5 minutes per shrub, or until I start to get runoff. When watering trees, water around the drip line, or ends of the branches, not right around the trunk. One way to accomplish this is to take a soaker hose, make a circle around the tree at the drip line, and turn it upside down. Let it run for an hour or more per tree until the soil is moist to a depth of 12 to 18 inches.
To determine how deep you are watering, take a large screwdriver or piece of rebar and push it into the soil. It will push in with little resistance to the depth you have watered, but will require more force to push it into dry soil.
For more information on fall lawn care, contact your local Nebraska Extension office.