Fall Turf Chores
Fall is time to think about applying fall preemergent herbicides to your lawns. Normally mid to late September would be the ideal time to apply your pre-emergent. This is a treatment that is often overlooked but can make a big difference on winter and spring yard weeds.
Preemergents should be applied now to help control winter annual weeds like rescue grass, ryegrass, annual bluegrass, and the dreaded henbit. Timing is critical for application of preemergent as they have little or no activity on weeds that are already actively growing when they are applied. It is also very important to water these pre-emergents into the soil so they will begin to provide control over germinating weed seeds.
Unfortunately, this application will do nothing for the two major weeds we are seeing in yards right now: grassburs/ sandburs and khaki weed. Sandburs are at their worst right now, however there is no postemergent herbicide that will control them. At this point, your best option is to dig or pull them up (being careful not to drop the burs) and dispose of them by burning, sending to the landfill, or spreading on your worst enemy’s lawn. Whichever method you choose, plan to use a pre-emergent early next spring to try and control them.
Often mistaken for burr clover, khaki weed is a weed issue that has exploded in the last few years. This weed is reddish and green, has thick waxy leaves, runners that will run 1’ to 2’ from the main plant, and of course burs. It is extremely invasive and hard to control. There is not a lot of information or research out there for controlling the plant. A mixture of 2,4-D, MCPA, and dicamba are about the best you will find in a homeowner mix to aid in control. Two products with these ingredients are: Bayer Advance weed killer for lawns and Ortho weed be gone. Check with your local lawn and garden or feed and seed store to see about other options. Glyphosate (Roundup) will also work, but it will kill everything it touches that is green.
Always read the herbicide label before purchasing or applying any pre- emergent herbicide. Labels do change and it is important to make sure the herbicide is still labeled for use in the type of turfgrass growing in your lawn.
This is also the time to apply your final fertilizer treatment of the year. Applying nitrogen in the fall increases the density of the lawn, helps it resist winter weeds, and improves fall color and spring recovery. For this application, use soluble, readily available nitrogen sources- I like to use ammonia sulfate (21-0-0) for this application. If you apply modest nitrogen rates (1 pound or less per 1,000 square feet), you will help the lawn and reduce the potential for nitrogen carryover and leaching during the winter.