Q. Is there anything that I can do to green up my tall fescue lawn? It was nice and green a month ago, but now it is quite yellow and tan.
A. First determine if your lawn is yellow because of recent frost, lack of fertilizer, or it has rust.
Many fescue lawns were nice and green up until the holidays, and then nighttime temperatures dropped into the 20s and 30s. Sudden cold temperatures caused frost damage to leaf blades. Damaged yellow and tan leaves will remain on the grass plant until temperatures warm up, the lawn grows, and the old leaves are mowed off.
Some lawns are yellow because nitrogen fertilizer is lacking and iron is unavailable due to cold soil temperatures. Mid to late February is a good time to apply a complete fertilizer for lawns so that the nutrients (especially phosphorus) are available to grass roots just prior to the spring growth flush.
It is also wise to make a topdressing application (less than one-quarter inch) of humus or fine compost (nothing too woody) and rake it smooth. The more uniform your application, the better your lawn will look. Spring rains will leach small amounts of nutrients into the soil over a sustained period of time and provide a deep lush green color. An added benefit of organic matter is it contains beneficial microbes that help break down grass thatch.
Rust in lawns is a disease that begins as small yellow spots on leaves and stems that develop into elongated reddish brown scabs loaded with red spores that stick to your shoes when you walk on the lawn. When the grass is growing slowly (like now in the winter) a fungicide that prevents more rust can be used, but is rarely really needed. The disease eventually diminishes as temperatures warm up especially when the lawn is fertilized, watered, and mowed regularly.
Q. Last summer my lawn had a lot of grassy weeds, especially crabgrass. What can I do to keep it from coming back?
A. By understanding the lifecycle of crabgrass and the best care practices for tall fescue, you can improve your success at weed control.
Crabgrass starts to germinate when soil temperatures warm up to 50°, which is around March 1. Weed germination continues throughout spring, summer, and fall producing plants and seed heads until soil temperatures start to cool down. Then crabgrass dies out for the year.
Crabgrass is usually a bigger problem in fescue lawns that are mowed too low and watered too often. You can watch crabgrass creep into sod lawns when they are a couple of years old. It starts on the edges and sides where string trimmers have cut the lawn too close. More light penetrates the exposed soil and the seeds germinate. As you mow you spread its seeds throughout your lawn, or your gardener brings it in from other clients. So make a change in your lawn care and start mowing fescue lawns at least 1.5 to 2 inches tall. Then regulate how often you water; water only when needed in early spring and water deeply. Now is the perfect time to get started for the spring season.
Crabgrass in lawns is easy to control with PREemergence herbicides but difficult to impossible to control with POSTemergence herbicides. For preemergence herbicides to be most effective it is best to apply them about three weeks before crabgrass germinates, for us that is between Super Bowl Sunday and Valentine’s Day. This applies to all types of lawns.
Try to time your application before a rain event. If no rainfall is forecast, then water the lawn thoroughly to activate the herbicide.
Preemergent herbicides containing benefin, bensulide, dithiopyr, oryzalin, pendimethalin, and prodiamine control crabgrass. Trade names such as Amaze, Crabgrass Preventer, Halts, Pendulum, Weed Stopper, Barricade, and Dimension may sound more familiar. Dimension also works on young crabgrass, whereas the other products do not.
All garden centers have a big selection of products for crabgrass. If you select a “weed and feed” make sure it contains a preemergence herbicide. Most of them only contain postemergence herbicides for controlling existing broadleaf weeds and have no effect on preventing crabgrass. It may take two applications per year (late winter and late spring) to clean up a crabgrass infestation, but herbicides should not be needed year after year, if cultural practices are modified to favor the lawn.
– Michelle Le Strange is a UC Master Gardener. To contact the Tulare/Kings Master Gardener Program, phone 684-3325, email email@example.com, or write to 4437 S. Laspina St., Suite B, Tulare, CA 93274.
– This column is not a news article but the opinion of the writer and does not reflect the views of The Foothills Sun-Gazette newspaper.