Winter Fertilization of Lawns

Pink Snow Mold

People often choose tall fescue over bermuda lawns as they want a year-round green lawn.  There is no great advantage to having a tall fescue lawn in the winter that looks anemic at best due to neglect.  People want green.  Lawns will battle cold soil temperatures, saturated soils, extended damp and foggy periods, frost, and occasional diseases like rust and pink snow mold.  This is not exactly hitting tall fescue’s sweet spot of sunny, 65-75 degree days seen in the spring and fall. 

If no fall fertilization occurs then the likelihood of having a green lawn in January and February is dismal.  Tall fescue lawns need a bit of a push heading into the cold weather.  It needs to be pushing new growth albeit slow.  No grow…no green.

Can you just put any fertilizer out there in the fall and expect decent color?  You will probably see a response from most any fertilizer, but the level of response in colder weather will change with the source of nitrogen in the fertilizer.  I am a strong proponent of slow-release fertilizers as they are less likely to burn in the summer months and they feed the plants over an extended period of time allowing for greater efficiency and uniform growth.  When it comes to colder weather and cold soils we need to look at products that are either readily available for root uptake or can be converted by microbes to an available form in a reasonable time period.  You may have noted that many of the winter fertilizers have some form of nitrate nitrogen in the blend.  Nitrate is readily available to the plant and will be the form that with yield the fastest response.  Urea and ammonium forms may take 2-10 weeks to be converted to nitrates for plant uptake.  These are normally quick-release products in warm weather, but act like a slow-release in winter months.  I do not see a great benefit to sulfur-coated or poly-coated products at this time of year as they will likely not be available until sometime in February or March.

Healthy Tall Fescue 

How about other nutrients?  I always like to see some phosphorus, potassium, and even sulfur in the mix as well.  They may not add much to the plant color, but they can encourage healthier roots and tougher cells walls to fend off temperature stresses and diseases, and make more nutrients available by lowering the pH, respectively.

From past experience it is difficult to have a perfectly green lawn in the winter months.  Some yellow leaves and occasional pink snow mold or brown patch may show up even with a good fertilizer program.  Doing nothing will likely result in poor color for a few months. On the positive side, a good spring feeding and warmer weather will restore your lawn to a great green in no time.

Is Your Lawn Getting a Little Rusty?

I know there has been a lot of excitement over the Giants winning the World Series, but the fact that some lawns are turning orange really has nothing to do with baseball.  The grass may exhibit some yellow spotting initially, but as the rust advances one will see a reddish-orange powder develop on the leaf surface.  These are the spores of a lawn infecting fungus (Puccinia sp.).  Mowers, shoes and clothing can become a magnet for picking up the rust colored spores as they pass across the infected lawn transferring the spores to other lawns that may be susceptible, especially if there is a bluegrass component to the lawn mix.  If you pass your fingers across the leaf blade you will likely have the orange spores deposited on your skin.  It will not hurt you…really.

The rust colored lawns tells me a few things.  First, there is likely some Kentucky bluegrass in the lawn as that is the most likely grass type to get rust.  Ryegrass and tall fescue may exhibit some rust in rare cases here in Central California.  Secondly, rust indicates that the weather has changed and we are in a period where the days are warm (70 to 75 F) and nights are getting cooler and damper.  Spore germination and infection of the rust fungus into host plants can occur with extended periods of leaf moisture lasting 10-12 hours from dew and/or irrigation.  Other conditions like lack of water, low levels of nitrogen, infrequent mowing, and mowing too short can certainly enhance the presence as well.  Rust was noted on lawns November through June this last year, but the peak occurrence was mid March and the month of April. 

Although it can be very visible and a bit unsightly, the disease rarely causes any notable damage to the lawn.  Application of a fungicide is not usually recommended when proper cultural practices are employed.  I would be sure that the lawn has been adequately fed with a fertilizer that will promote new growth thus allowing the infected leaves to be cut and removed.  Secondly, I would make sure the lawn has sufficient water available to favor good growth and water in the early morning so that the period of wetness does not get extended further into the day.  Finally, I would make sure that the lawn is mowed weekly at 2.5 inches or higher.