Winter Weeds
Amy Jordan
Thursday, November 2, 2006
Cool-season turfgrass, such as tall fescue, responds well to a little attention in November.
Its a great time to control weeds and help the grass to get a jump-start next spring.
Winter-annual weeds, such as henbit and chickweed, are usually most noticeable in spring when they are fully mature. Winter-annual means they germinate in the fall (usually October through early November), live throughout the winter and spring, then complete their lifecycle in late spring as the weather warms. It is difficult to control them in spring, but they are easily controlled this time of the year with a broadleaf weedkiller. If these weeds are growing in a flower bed, they can be lightly cultivated for control.
Dandelions may have sent out a flush of new plants in September. These weeds are storing food reserves for growth next year. Because they are translocating food reserves to the roots, herbicides are very effective by also going directly to the roots. Fall application of herbicide to dandelions is typically much more successful than spring applications for this reason. In the spring, energy is spent on top growth instead of root growth.
Carfentrazone is a herbicide that is used in combination with other broadleaf weedkillers such as 2, 4-D, MCPP and Dicamba. It is a good choice for application when temperatures are below 50 degrees. It also seems to be effective on clover. Carfentrazone is found in products such as Weed Free Zone and Speed Zone. With all broadleaf herbicides, use caution where seedling grass is present.
Because November is a good time to fertilize tall fescue lawns, as well as apply herbicides to broad-leaved weeds, it is an appropriate time to use a “weed and feed” fertilizer/herbicide combination. Be sure to follow the label instructions which usually indicate that these products should be applied when the leaves of the weeds to be killed are wet so the herbicide particles will adhere to the leaf surface long enough for the chemical to enter the leaves; pre-wetting may be required. If crabgrass has been a problem in the past, consider using a fertilizer containing “Barricade”. Barricade is a pre-emergent herbicide that has a long residual and will provide control of emerging crabgrass plants next spring. Keep in mind the best defense against weeds is a dense stand of grass mowed at 3 to 3 and 1/2 inches. Mowing at this height will shade the soil surface, preventing weed seed from germinating.
To aid in growth and help the turfgrass store carbohydrate reserves for next spring, apply one to one and a half pounds of actual nitrogen per 1000 square feet. This will help the grass to green up earlier next spring, and sustain growth into May without the need for early-spring (March or April) fertilizer. Those early-spring nitrogen applications are less desirable because they can lead to excessive shoot growth and reduced root growth. Other benefits of November-applied nitrogen for cool-season grasses include improved winter hardiness, root growth and shoot density.
- Amy Jordan is a horticulturist with K-State Research and Extension in Lyon County.