WHY CAN’T I KILL THAT WEED IN MY YARD?

BY GEORGE EDGAR

           The experts on Backyard Farmer and the instructors in the Master Gardener classes always talk about having the “Right Plant in the Right Place. “The Right Plant in the Right Place” means you plan ahead and if you have a particular location you want filled, you select a plant that will be the right height, the right width, and needs the kind of soil you have. You also take into consideration the moisture and sun requirements. Or you start with a particular plant you bought or want to buy and select the location with the right amount of sun, the right amount of moisture, and has the room for the plant to grow to its mature height and width.

          The same approach applies to weeds. We say that a weed is just a plant out of place. (Right now I haven’t found the right place for “Crabgrass” or “Bindweed” but I suppose there is one.) For example, we have “Bromegrass” in the “Back 40” which is 300 feet by 150 feet between my lot line and Antelope Creek. It does not get any water other than rain, and does not get fertilizer. It was very brown during the drought in July and I thought sure it was dead, but when we got a 3 inch rain it greened right up. “Buffalograss” might take a little less mowing and be somewhat better, but would be expensive to replant the whole area now, and would not be green in the early spring or late fall. So for now, the Bromegrass is the right grass in the right place.

          However, when the “Bromegrass” roots cross that imaginary line between the “Back 40” and my vegetable garden, it becomes a weed. I know what this weed is and how to control it. But if you don’t know what your “Plant out of Place” (the weed you don’t like) is in your yard or garden, or how to control it, take a sample (more than one leaf) to a full service garden center that has a certified nursery person or a person trained in weed identification and control. Or take it to your local County Cooperative Extension Educator. Identification of the weed you are trying to kill is important and the first thing you should do.

“USE THE RIGHT PRODUCT, ON THE RIGHT PLANT,

AT THE RIGHT TIME!!!”

          Also it is helpful to know the life cycle of the weed. By life cycle I mean is it an annual or a perennial? Does it grow from seed or does it spread from runners, or both?  If it produces seeds, when do they mature, and then what time of year do they germinate? Also, can the weed seeds be controlled by a pre-emergence herbicide? Timing in the application of a herbicide is very important and knowing the life cycle of the weed helps us to know what time of year to apply the herbicide, what kind of herbicide to apply, and how often to apply.

                    The most common weeds found in our lawns, flower gardens, and vegetable gardens can be grouped as follows:

·       Annual grasses such as Crabgrass (Digitaria sanguinalis), Annual Bluegrass (Poa annua), Foxtail (Setaroa glauca) and Goosegrass (Eleusine indica).

·       Annual Broadleaf weeds such as Prostrate Spurge (Euphorbia supina), Spotted Spurge (Euphorbia maculata), Black Medic (Medicago lupulina), Pennycress (Thlaspi arvense), Purslane (Portulaca oleracea), Henbit (Lamium amplexicaule) and Common Chickweed (Stellaria media).

·       Perennial broadleaf weeds such as Dandelion (Taraxacum officinal), White Clover (Trifolium repens), and Ground Ivy (Glechoma microcarpa).

·       Perennial grasses such as Bromegrass (Bromus inermis), Rough Bluegrass (Poa trivialis), Tall Fescue (Festuca arundinacea), Nimblewill (Muhlenbergia schreberi) and Quackgrass (Agropyren repens).

·       Perennial sedge such as Yellow Nutsedge. Most people call it “Nutgrass” but it is really a sedge so does not respond to weed killers like a grass.

          Correct identification of the weed is important as use of the wrong weed killer may kill everything or may not kill the weed you want to kill. I have heard some people say that when they applied a specific product it seemed to make the weed grow faster. That may be true, as some weed killers such as 2-4-D are really growth regulators. They work by making plants grow so fast they die, just as too much nitrogen fertilizer on your lawn at the wrong time will burn it and may kill it. So, if you don’t have the right product, on the right plant, you may only encourage the growth of the weed and not kill it.

          Be aware that after identification, and knowing about the life cycle, one herbicide (weed killer or preventer) will not kill or prevent everything we call a weed. And some herbicides are ok for the lawn but should not be used in the vegetable garden. Also some herbicides kill the weeds (post-emergence) and some herbicides prevent the seeds from germinating (pre-emergence).

“USE THE RIGHT PRODUCT, ON THE RIGHT PLANT,

AT THE RIGHT TIME!!!”

          Some of the most common herbicides include:

·       Trimec (Earl May Weed Killer, Ortho Weed-Be-Gone, and Ortho Chickweed, Spurge, & Oxalis Killer) is a broadleaf weed killer and will kill Dandelions, Common Chickweed, Black Medic, Purslane, Ground Ivy, and Henbit but will not kill Bluegrass, Turf Type Tall Fescue, Bromegrass, Buffalograss, or Crabgrass. Triclopyr and Clopyralid are also broadleaf weed killers that are effective on most of the above weeds.  

·       MSMA (Monosodium methanearsonate) will kill Crabgrass and Yellow Nutsedge (Nutgrass) but will not kill Bluegrass and Turf Type Tall Fescue.

·       Manage will kill Yellow Nutsedge (Nutgrass) but not Crabgrass, Bluegrass, or Fescue. 

·       Fluazifop (Acme Grass-No-More, Ortho Grass-B-Gone) will kill many annual grasses and some perennial grasses in your flower bed such as Bluegrass, Tall Fescue, and Quackgrass, but will not kill many flowers such as Iris, Geranium, Daylily, and Peony. Will also not kill many shrubs, trees, cactus, and green fountain grass (ornamental grass) if applied as directed in the instructions.  

·       Glyphosate (Kleen-up, Round-up) will kill many green plants including trees, shrubs, flowers, and grasses but won’t kill Purslane, Prickly Pear Cactus, and many succulents.

“USE THE RIGHT PRODUCT, ON THE RIGHT PLANT,

AT THE RIGHT TIME!!!”                    

  For more information on lawn weed control go to http://ianrhome.unl.edu/search. In the top box scroll down to “Extension Publications” and in the bottom box type in G1045 or “Weed Prevention and Management”. Listed will be publications you can read, and/or print for reading later and for reference. Or go to http://lancaster.unl.edu for garden and lawn information, good tips, and access to other websites.

          In writing this article I also used “Integrated Turfgrass Management for the Northern Great Plains” by Frederick P. Baxendale, Ph.D. & Roch E. Gaussoin, Ph. D. (members of the University of Nebraska Turfgrass Science Team). Published by the Cooperative Extension Service, Institute of Agriculture and Natural Resources, University of Nebraska: 1997.

Copyright Sept. 10, 2005