Henbit, chickweed, annual bluegrass, smooth brome and shepherd purse winter weeds have not sprouted in your lawn yet but now is the time to prevent them. The best time to control these winter weeds is between mid August and the end of September each year with a pre-emergent herbicide. Think of the pre-emergent herbicide as birth control for your winter weeds. The seed is still there but the herbicide creates a barrier at the soil surface. This barrier prevents most of the weed seeds from germinating. Once the seeds have germinated the pre-emergent herbicide will not be effective so that is why it is important to apply it early enough to stop the seeds from sprouting. We have been so moist this year that some of these seeds may sprout earlier than normal. This year it is probably a good idea to apply the pre-emergent as soon as possible. Once the seeds have germinated the pre-emergent herbicide will no longer be effective and you will have to use a post-emergent to burn back and control these cool season weeds.
Herbicide, by the way, is a term descended from latin that means to kill herbs or weeds. Most of these winter weeds germinate when the temperatures start to cool and there is sufficient moisture for sprouting. The cool season weeds don’t grow real fast in the early winter but get well rooted and surge in growth in late winter and early spring when the temperatures start to rise again. In the early spring when winter weeds are well established they actually can compete with your desired lawn grasses for space, light, moisture and food. This can weaken your bermuda or chosen turf grass and can result in bare spots, stunting or leave your lawn more susceptible to invasions by crabgrass or summer weeds.
Your pre-emergent will be most effective if you mow the lawn before applying and remove debris and lawn clippings if very thick. The goal is to get the herbicide granules or spray through the turf foliage and to the surface of the soil. The pre-emergent works best if you get a half inch or more of rain within forty-eight hours of application. If it doesn’t rain within two days you should soak the lawn by hand or with a sprinkler to deliver the equivalent of a half inch of rain to water the herbicide into the soil where the weed seeds are laying and waiting to sprout. Most pre-emergent herbicides remain active for sixty to one hundred twenty days or two to four months. In some more severe cases you may want to make a second application in six to eight weeks for full control to next spring. There are many good herbicides on the market and it is always a good idea to divide the labeled amount into two batches and apply half going north /south and the other half in an east/west pattern to insure good even overlapping coverage. Most of the fall pre-emergent herbicides we apply in this area are available with a fall fertilizer and are marketed as weed and feed products. This is a good time to do the last lawn feeding of the season while applying your pre-emergent weed killer to prevent cool season weeds. Ask for a pre-emergent weed killer containing Dimension, Balan, Treflan, Barricade, Sulfentrazone or Simazine for best results.
This is also a good season to fertilize your trees and shrubs. Use a well balanced food where the three fertilizer numbers for nitrogen, phosphorus and potash add up to over twenty. This is a good time to lightly prune or shape your hedges and shrubs. Be on the lookout for fall webworms on your trees and shrubs and spray with carbaryl (Sevin) or bacillus thuringiensis (Dipel) for control if you are not able to just cut off and throw away the webbed branches. If you plan to sow tall fescue lawn seed in mid September to late October you can go ahead and spray that area with a glyphosate (Round Up) product to kill the competing grasses and to get ready for your winter fescue.
For those of you doing fall vegetable gardens we are in the last phase of the fall vegetable planting season where you can still plant cool season vegetables cabbage, cauliflower, collards, garlic. kale, kohlrabi, leek, onions, peas, radish, rutabaga, swiss chard and turnips of the semi hardy vegetables that will survive several light frosts. You can still plant a few tender vegetables and still get a crop before our first serious freeze. That group includes bush beans, lima beans, cucumbers and summer squash.
As the temperatures start cooling later in September we enter the prime season for planting trees, shrubs, hardy mums, pansies, ornamental kale and cabbage. It seems like this year we have been zigging and zagging between a barrage of heavy rains and hot humid days. Celebrate the pretty days to get out in the yard and get some exercise while growing some fresh food and beautifying your yard.
Rodd's Seeds of Wisdom 