Start Your Battle With Summer Weeds Now

February 19, 2011

theresafriday.jpgWeeds are problematic in most landscapes.  Even if you do everything right, a weed is going to pop up occasionally in the lawn.  Although most of our lawns are still dormant, it’s time to decide if you need to apply a pre-emergence herbicide (weed preventer).

Weeds can be less of a problem if you maintain a healthy lawn through proper cultural practices.  Watering correctly, using appropriate fertilizers and maintaining a high mowing height will ensure your lawn is at its peak and can compete with the weeds.

However, if year after year you have an abundance of weeds during the summer, a pre-emergence herbicide may help you in the battle against weeds.

Pre-emergence herbicides are applied before weed seeds germinate.  Therefore, it’s critical that these chemicals be applied at the proper time.

In Northwest Florida, timing of a pre-emergence herbicide application for summer annual weeds, such as crabgrass, should be between February 15 and March 5 or when day temperatures reach 65 to 70 degrees F for four to five consecutive days. This generally coincides with the blooming of azaleas and dogwoods.

Some pre-emergence herbicides to look for include:

  • dithiopyr (Dimension)
  • isoxaben (Fertilome Broadleaf Weed Control with Gallery)
  • pendimethalin (Lesco PRE-M or Scotts Halts Crabgrass Preventer)
  • benefin (Hi-Yield Crabgrass Control)

Be sure to apply any product according to the label directions.  Even, consistent coverage is essential with pre-emergence herbicides.  Any gaps in coverage will allow weeds to emerge.

Once applied, be sure to water-in the product.  Do not apply before a rain event.  It’s hard to know how much rain will fall at any one time.  Too much rain can send your weed killer down the storm drain.

Pre-emergence herbicides are generally effective in controlling weeds from six to twelve weeks following application.  Most will begin to degrade when exposed to the environment. Therefore, to obtain season-long control, an additional application should follow six to nine weeks after the initial one.

It is possible to use too much pre-emergence herbicide.  Some pre-emergence herbicides have a root-stunting effect on established turf and can thus be detrimental to the health of your lawn if applied at too high of a rate or applied too many times during a season. It is best to time applications when they will be most effective, and to further prevent weeds by maintaining a dense, healthy stand of turf.

It is difficult to find a good time to apply “weed-n-feed” products. Weed control using pre-emergence products should be applied from mid-February to early March. Fertilization should wait until your lawn if fully out of dormancy and actively growing.  In our area, that is sometime in April.

When nitrogen-containing fertilizer is applied too early to warm-season grass, it may stimulate the lawn to grow much too soon.  If we have a couple of weeks of warm weather followed by a late frost, damage can occur to over stimulated lawns.  My recommendation would be to apply your pre-emergence herbicide separately from your nitrogen-containing fertilizers.

If weeds have been a major problem in your landscape consider using pre-emergence herbicides.  If applied at the proper rate and at the proper time, the benefits can be tremendous.

Theresa Friday is the Residential Horticulture Extension Agent for Santa Rosa County.

Comments

2 Responses to “Start Your Battle With Summer Weeds Now”

  1. Francis Clark on September 23rd, 2015 10:35 am

    I usually apply Dimension for weed control in the fall and late winter here in Escambia County. What are the best dates on either end of the calendar?

  2. A thankful person on February 20th, 2011 3:31 pm

    THANKS! I purchased weed and feed today. Will store it until proper time and buy some “benefit”. Anyone know who sells it?

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