As we approach Thanksgiving it is a good time to start thinking about your winter fertilizer program. In past blogs I talked about getting down a few fertilizer applications prior to the first frost of the year. In general we will receive our first frost sometime between Thanksgiving and the first week of December. The first couple of frosts are usually pretty mild, but as we get deeper into December we will get some hard freezes which will start to affect your roots. Once we get frost all the way down to the roots it makes it tougher for the plant to take up fertilizer so foliar applications generally provide the best response.

For those unfamiliar with why plants freeze let me provide you with a simplistic definition.  Water vapor condenses into liquid water and forms ice as the temperature drops at or below 32 degrees. Temperatures on the ground are typically cooler than the air just a few feet above the ground surface. On a clear, calm night with no little wind the cold air sinks to the ground level and while the thermometer may not read 32 degrees or lower, the ground temperature is below freezing. You will notice that when there is a heavy cloud cover there is typically no frost. This is because the grass does not need to emit as much radiation because the clouds reflect the radiated heat. On a cloudy day dew will form on the ground making it very unlikely that frost will form on the ground.


With the onset on frost you will start to see some loss of color in your grass plant. If you properly “juiced” up your lawn with fertilizer after you seeded then you should still have good color. If you were only able to get one or two fertilizer applications down prior to the frost you will notice that some of the leaf tissue is starting to turn brown and yellow. Often times this is just the warm season grass that was hanging around finally going dormant, but other times you need to get some fertilizer on the ryegrass. One of the best secrets in the turf industry is using ferrous sulfate and potassium nitrate to spray on your grass. This mixture will not only provide nitrogen to the grass plant it will also keep the ground warmer because of the dark color. The ferrous sulfate will leave the grass with a sticky feel and has a tendency to turn the leaves black for a couple days which traps the heat in the grass. This black color will quickly change to a green lawn after a couple days and should provide your lawn nutrition for the next month. This application should be made every 3-4 weeks during the winter in order to maintain a dark green lawn. If you cannot find these products I would look for a foliar spray that is high in iron and will also provide a good source of nitrogen. You can often find mixtures of calcium and ammonium nitrate which will provide very good color. These products are generally available at a nursery or an irrigation specialty store such as Sprinkler World.

If you have chosen to let your lawn go dormant for the winter now is a good time to shut your water down. There is no need to water anymore than once every couple weeks and by mid-December you can cut it down to monthly until February.

Hope everyone has a great Thanksgiving, and may your teams win!  As always, if you have any questions please hit the “Ask Jay” button on the top right of this page and I will do my best to help.