Kali Zammit, Schmit, Rene G. | 1/22/2013 9:49:16 PM
Although lawn grasses and landscape shrubs are dormant this time of year, they will continue to utilize soil nutrients that benefit their ability to over winter more efficiently. Weeds that become invasive can interfere with that important process and benefit. Therefore, the control of weeds in lawns and in landscape beds is as important during the winter months as it is any other time of the year.
When weeds are allowed to remain and flourish over long periods of time, they can become quite difficult to remove by hand. The alternative often requires the use of a post-emergence herbicide to kill them and usually requires more than one application to achieve an effective kill. Products such as Vantage (sethoxydim), Image (imazaquin), Ornamec or Grass-B-Gone (fluazifop) are post-emergence herbicides that can be used safely in landscape beds however; each product is selective meaning they are formulated to kill specific type weeds. Vantage, Ornamec or Grass-B-Gone, for example, will control only grasses while Image will control some of both grasses and broadleaves. Glyphosate products such as Roundup and Killzall are also safe for use in landscape beds and are non-selective meaning these products will control a wide range of grass and broadleaf weed species.
In addition to using a post-emergence herbicide, the use of a pre-emergence herbicide will also aid in controlling weeds in landscape beds. Types of pre-emergence herbicides that are available for broadcast use in landscape beds include Amaze (benefin) and Preen (trifluralin) which are granular herbicides. These pre-emergence products do a very good job in preventing many weed seeds from germinating but work best when applied to landscape beds every 3 months and in combination with post-emergence herbicide spraying and mulching. When using a chemical herbicide make sure to spray only the weed and not the ornamental as severe injury or death could occur. One method for prevention is to take a pliable poster board and shape it into a cone cylinder. Place the cylinder over the weed then aim at the weed and spray. Wait 5 seconds before removing the cylinder to allow the spray to settle.
In lawns various broadleaves such as oxcillus, clover, dandelion, Carolina geranium and dollar weed can become quite invasive this time of year. Effective control can be accomplished by using tri-mec formulated herbicides such as Weed-B-Gone Max, Weed Free Zone, Bayer Southern weed Killer, or Spectrum 33 Plus, just to name a few. Be sure to always apply tri-mec herbicides during morning hours when there is no wind and when ambient temperatures are within the range of 60 to 80 degrees Fahrenheit. Again and quite often, multiple applications may be needed. By controlling winter weeds now you can provide the opportunity for your lawn and landscape plantings to achieve a healthier start and performance come spring.Rene’ Schmit is the St. Charles Parish County Agent of the LSU AgCenter and can be reached at 985-785-4473.