Control broadleaf weeds in lawns in late October to early November
Late October to early November is the most effective time to control broadleaf weeds in lawns. Dandelions usually produce a flush of new plants in late September, and the winter annual weeds henbit and chickweed should have germinated in October.
These young plants are small and easily controlled with herbicides such as 2,4-D or combination products (Trimec, Weed-B-Gon,Weed-Out) that contain 2,4-D, MCPP and Dicamba. Even established dandelions are more easily controlled now than in the spring because they are actively moving materials from the top portion of the plant to the roots in the fall. Herbicides will translocate to the roots as well and will kill the plant from the roots up.
Choose a day that is 50 degrees or higher. The better the weed is growing, the more weed killer will be moved from the leaves to the roots. Cold temperatures will slow or stop this process. Weed Free Zone (also sold under the name of Speed Zone) contains the three active ingredients mentioned above, plus carfentrazone. It will give a quicker response than the other products mentioned especially as temperatures approach 50 degrees.
Apply Late-Season Nitrogen Application in November
November is the time to give cool-season lawns the last nitrogen application of the season. Why November? Because while top growth slows in response to cool temperatures, grass plants are still making food (carbohydrates) by photosynthesis. A November nitrogen application helps boost the photosynthesis rate.
Carbohydrates that are not used in growth are stored in the crown and other storage tissues in the plant. These carbohydrate reserves help the turfgrass green up earlier in the spring and sustain growth into May without the need for early-spring (March or April) nitrogen. 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.
How much should you apply? One to one and a half pounds actual nitrogen per 1,000 square feet of lawn area is sufficient. In order for this application to be effective, the nitrogen must be readily available to the plant because the growing season is nearly over. Therefore, for a November application, use a soluble (quickly-available) nitrogen carrier such as urea or ammonium sulfate.
Many turfgrass fertilizers sold in garden centers and other retail outlets also contain soluble nitrogen. Avoid products that contain water-insoluble nitrogen (slow-release) for this application. As always, sweep up any fertilizer that gets on driveways, sidewalks, or streets and reapply it to the lawn.