Dr. Grow: Fall fertilizing can help prevent spring weeds

Application of a crabgrass-control herbicide plus lawn food can keep many fall-germinating weeds from emerging. (Fred Lynch) [Click to enlarge] [Order this photo]

My traditional recommendation for fall fertilization of a cool-season lawn starts with an application of high-nitrogen fertilizer, such as a 28-0-4, in early September. You can also make this same application on warm-season lawns if you do it in late August. At this time of the year soils are often warmer than air temperatures, so the fertilizer encourages lawn grasses to produce an abundance of roots.

In addition, I suggest to lawn owners that they apply trimec, a combination of three herbicides that kill broadleaf weeds, in October. This application is usually needed because dandelions and other broadleaf weeds tend to seed themselves in September or October after fall rains begin. A broadleaf application at this time of the year will eliminate these troublesome weeds before they rear their unwanted heads in the spring.

The seeds of annual broadleaf weeds, such as chickweed and henbit, also germinate in late September or October. The actual germination time depends upon rainfall. If these weeds are allowed to grow, they can easily turn a lawn or a shrub bed into a mass of purple early in the spring. A late fall application of trimec will usually eliminate these weeds.

There are two problems associated with the above program. You can't use trimec in a shrub bed, because it will kill or damage desired perennials, annuals and shrubs. Secondly, lawn owners often forget or don't make the late trimec application because busy fall schedules do not give them a window of opportunity.

I have been in the lawn-care business for so many years that I just took the above program for granted. Because my formal training was in forestry, I guess you could say that I couldn't see the forest for the trees. Perhaps in this case I couldn't see the lawn for the grass.

After talking about the standard fall application for Southeast Missouri lawns, my co-worker Tina suggested that lawn owners should apply a crabgrass-control herbicide plus lawn food in early September. The crabgrass-control herbicide will keep many fall germinating weeds from emerging. That would eliminate most of the henbit, chickweed and annual bluegrass. This application can be made to lawns and shrub beds.

By using the crabgrass herbicide in combination with a high-nitrogen fertilizer (a combination found in most crabgrass-control-plus-fertilizer combinations sold in the spring), you can often get both weed control and fertilization in one application. This could eliminate that late October spray application for broadleaf weeds.

As my grandfather used to say, "There is more than one way to skin a cat." Give this application a try and see if your lawn doesn't look a lot better in the spring.

Send your gardening and landscape questions to Paul Schnare at P.O. Box 699, Cape Girardeau, MO 63702-0699 or by e-mail to news@semissourian.com.<I>