Rotating Extension Article

For: Week of February 18, 2002

By: Dan Mullins

Extension Horticulture Agent

Santa Rosa County

Spring Lawn Weed Control Considerations

This is the time of year that homeowners and gardeners’ thoughts turn to controlling weeds in the lawn. Before purchasing and applying a weed killer there are several important questions that should be answered.

Question: Am I dealing with winter or summer weeds?

This is an important consideration. Weeds that are actively growing in February are cool season or winter weeds that germinated last fall. They are now making a final flush of growth and are preparing to flower and produce seed.

Since winter weeds are now nearing the end of their life cycle, most of the so called “weed and feed” products would have little or no effect. With a few exceptions, these combination type products are formulated to either prevent weed seed germination or kill very young seedlings. To control winter weeds at this time of year hand pulling or the application of a post-emergent herbicide is required.

Question: If I want to control warm season or summer weeds, when is the best time to apply a pre-emergent herbicide?

Use a pre-emergent herbicide only if you have a history of summer weeds that can’t be controlled by hand pulling and through the use of other cultural practices. Timing is everything when applying this kind of product. A general rule of thumb for application is March 1 for North Florida. However, the proper timing can vary with the weather.

Technically, spring weed seed germination begins when day temperatures reach 65 to 70 degrees for 4 or 5 consecutive days. The right timing usually coincides with the blooming of azaleas and dogwoods.

Question: How can I choose the right product?

Read the herbicide or “weed and feed” label carefully. There is some important information there including type of action - either pre-emergent or post-emergent. It will also describe the species of weeds that are controlled, recommended time of application and if it can be safely applied to your kind of grass.

When using weed and feed products it is equally important to know about the fertilizer component of the mixture. In some cases, the rate that is recommended for the herbicide portion might not contain the optimum fertilizer rate or analysis for local conditions. Under such circumstances it might be more practical ro apply a selected fertilizer and herbicide separately.

Turfgrass products containing herbicides should be used with caution near flowers, shrubs and trees. Those that contain dicamba, metsulfuron or atrazine can be absorbed by the roots of ornamentals and cause severe injury. Necessary warnings and precautions will be included on the label.

If you need further help with weed identification and recommendations concerning control contact your Florida Extension office, lawn care professional or a reputable garden supply store.

Extension Service programs are open to all people without regard to race, color, sex, age, handicap or national origin.

Dan Mullins is Extension Horticulture/Vegetable agent for Santa Rosa County.