You wouldn't think your lawn does much when it gets cold. Even though you have stopped mowing, however, the grass roots continue to be active. University of Guelph studies show that a late season application of fertilizer will enhance winter hardiness and survival and also increase the early greenup of your lawn in the spring.
Here is a synopsis of an article by Pam Charbonneau (OMAF Turf Specialist adapted from Turf Notes).
Winterizing Turf Low temperature injury
Now is the time to think about putting your lawn to rest for the winter. In order to understand what needs to be done to avoid winter kill, one needs to have a good understanding of what winter kill is. Winter kill can be caused in three different ways: Direct low temperature stress, winter desiccation, and injury caused by low temperature fungi. What mechanisms do plants have for achieving winter hardiness? The turf grass plant becomes more winter hardy by storing sugar in its cells and hence lowering the amount of water in the plant. A cell with a high sugar content is more resistant to freezing than one with a low sugar content. A good analogy is a bottle of juice taking longer to freeze than a bottle of water. We need to help the grass store more sugar in its cells.
Cultural Practices -The key principle is maintaining a low level of water in the crown of the plant. Several cultural practices accomplish this:
1. The first step in the prevention of low temperature injury is to provide adequate surface drainage. Grass surrounded by water in winter will take up water. This extra water makes it prone to internal freezing.
2. Controlling thatch is also important. Thatch harbours disease-causing organisms such as snow moulds. Also, with excessive thatch the crowns are elevated above the soil and are exposed to greater temperature extremes. (Aerate to reduce thatch. See Turf Facts on Aeration & Thatch)
3. Raising the mowing height makes the crown less exposed to extreme temperatures. Also additional plant material serves as insulation for the crowns. However, do not abandon mowing as excessively long grass is a perfect environment for low temperature fungi.
4. Adequate levels of potassium, phosphorus and nitrogen are important in ensuring winter hardiness. Late season fertilization 1. Nitrogen is taken up by the roots even though the lawn has stopped growing on top. Roots remain active at lower temperatures than shoots. 2. Nitrogen enhances fall colour and hence increases chlorophyll (the green part of plants). 3. Increased chlorophyll means increased photosynthesis. (the manufacturing of food i.e. sugars) 4. Increased photosynthesis means increased sugars. Since the grass is not growing at this time, the sugars are not used for growth but are stored to enhance winter survival and spring recovery.
5. Late season feeding promotes deep rooting in the fall. Plants go into the spring with deeper, healthier roots.
6. Spring greenup is earlier because the nitrogen and nutrients are stored in the roots and are ready to be used when shoot growth resumes. Timing Winter fertilizer should be applied when the grass is green but no longer growing; too early and it will produce lush succulent growth; too late and it will be of no benefit. Generally late October through mid-November is the best time. These studies have given these results using a high Nitrogen slow release fertilizer similar to Turf King's fertilizer. Lawns receiving Turf King's Winter fertilizer will have increased winter hardiness and will green up very early in the spring.
If you have a lawn/tree/shrub that needs some Tender Loving Care- get The KING OF GREEN: