William Hogan | 9/15/2011 6:35:41 PM
Most of our lawns have had a rough summer. The early summer drought kept many from reaching their early season potential. Lots of home gardeners irrigated more than was their normal custom. The grass didn’t look too good, but they kept it alive. In July, we received normal rains. In August, we had another drought. Tropical Storm Lee dumped a month’s worth of rain during the Labor Day weekend. It has been quite a roller coaster for lawn grass this summer. In spite of all this, most lawns are in pretty good condition going into the fall or dormant season. There are several management practices we can utilize in the fall to increase the vigor of our lawns for next spring and summer.
Fall Lawn Weed Management
Preventing weeds from establishing themselves in the fall can make for a cleaner lawn in the spring. Most of the weeds that we first notice in late winter and early spring actually germinate in October and November. They remain small and unnoticed through the winter and begin to grow in early spring before our lawn grass breaks dormancy. Preventing them from establishing themselves saves you the problem of control later in the year. Dr. Ron Strahan, LSU AgCenter Turf Specialist, recommends pre-emergence herbicides applications in late September and again in mid-November. For prevention of many annual broadleaf weeds and bluegrass (winter grass) he suggests Scotts Halt, Hi-Yield Weed Stopper or Green Light Crab Grass Preventer. Green Light Portrait gives good control of many winter annual weeds, but is not effective on grassy weeds. Water the herbicides into the lawn or apply just before a rainfall. Avoid using an herbicide that comes pre-mixed with nitrogen fertilizer.
Fall Lawn Fertilization
Should you fertilize in the fall? That depends on the nutrient content of your soil. If your soil pH is 6.2 or higher, you can apply phosphorus and/or potassium fertilizers. If your soil pH is less than 6.2 (more acid), these nutrients will probably be bound to the soil in such a way that the plant won’t be able to use them next spring. Since the grass is going dormant, the fertilizer won’t give much green color improvement between now and winter. It is probably most practical to delay phosphorus and potassium applications until next April. At that time apply phosphorus and potassium according to soil test recommendations.
Nitrogen applications in the fall can also increase brown patch disease. Brown patch disease is caused by a fungus that requires free moisture, mild temperatures and nitrogen. It is most common in the fall. It is also most severe at this time of year. Avoid nitrogen fertilizer application to lawn grass (especially St. Augustine) between September and April.
As you can see, it is difficult to make up for poor fertility in the fall. A more efficient program is to apply the fertilizer in spring, when the grass can utilize it better. There are special cases that benefit from fall fertilization. Over-seeded perennial ryegrass into the lawn is one such case.
Ryegrasses in the Lawn
There are advantages to having ryegrass in your winter lawn. It gives a lush, green appearance during a cold and generally drab time of year. Ryegrass is also an excellent competitor with winter weeds. It discourages the growth of clovers, burweed and many of the “sticker weeds” that infest many yards in spring. However, ryegrass may also delay the emergence of your summer lawn grass. An additional disadvantage is having to mow a lawn twelve months of the year.
Plant ryegrass in the lawn in mid-October through November. Be sure that your summer lawn grass is dormant. A wet, warm period of weather can cause the summer grass to out- compete the seedling ryegrass. Mow the lawn one-half inch shorter than normal before planting. Sow or broadcast ryegrass seed at 5-10 pounds per 1000 square feet of lawn. If St. Augustine is the sod, be sure to use the higher seeding rate, 8-10 pounds of seed per 1000 square feet. After the seed is broadcast, rake or drag the seeded area to increase the seed to soil contact.
Be sure to plant a perennial or turf type ryegrass. These have a fine leaf and do not tiller or form clumps as much as the forage type of ryegrass. Turf types also tolerate cold weather very well. Their growth habits are better suited to lawns, even though they are more expensive. They are worth the extra expense compared to the pasture types of ryegrass.
Ryegrass is very sensitive to soil pH. It will be healthier and have better color if your lawn soil is in the pH range of 6.2-6.8. A simple soil test will determine the pH of your soil and recommend how much agricultural lime is needed to correct too much soil acidity.
After the ryegrass emerges, or about one month after planting, apply 8 to 12 pounds of 13-13- 13 fertilizer per 1000 square feet of lawn. Delaying fertilization until this time will help prevent the summer grass from re-growing and competing. If your ryegrass needs growth stimulation in the winter, apply three pounds of ammonium nitrate per 1000 square feet in the January-February period of time. This is usually not necessary in most lawns.