Giving Perennial Weeds a One-Two Punch
No matter how hard you pull, how often you spray or how loud you scream, some weeds always seem to pop up in your lawn. These are most likely perennial weeds, which live more than one year (much like grasses) and can be quite difficult to eliminate. Here are some tips on how to control the top five "perennial pests," including ground ivy, quackgrass, yellow nutsedge, torpedograss and dallisgrass.
Ground Ivy
Also known as creeping charlie, gill-over-the-ground or run-away-robin, ground ivy (Glechoma hederacea L.) is a prostrate creeping weed that looks like it escaped your flower bed and lost control in your lawn. It prefers to live in shaded areas where it is difficult to grow grass, so it has less competition to keep from flourishing. Ground ivy can be identified by its blue- to purple-colored flowers that bloom in the spring.
You can control ground ivy in the spring or fall, but this weed is extremely difficult to combat in the summer. Most experts suggest repeat applications of a three-way herbicide combining 2, 4-D, mecoprop and dicamba. Studies show that adding quinclorac, a registered herbicide known as Drive®, to this three-way herbicide will knock out ground ivy. Fortunately, there is another effective herbicide that can be purchased at garden stores — a purple-labeled product called Ortho® Weed-B-Gon® containing triclopyr. You may need to stagger applications about two weeks apart, but in the end, your lawn will be liberated from creeping charlie.
Quackgrass
Quackgrass (Agropyron reptans L.), also known as creeping quackgrass, is tough to eliminate because of its underground rhizomes, the plant stems in the soil underneath the grass, which help the weed spread and survive. This weed often thrives in areas of a lawn that have recently been disturbed or stressed.
No known available herbicide exists that will selectively remove quackgrass from cool-season grasses. To eliminate this weed, use a non-selective herbicide such as glyphosate (found in Roundup® or Finale®). These herbicides kill anything green, so you may end up with one big bare spot on your lawn. To prevent the "spot disease," take a small paint brush and literally paint the herbicide on the leaves. It is tedious, but so is living with unsightly quackgrass.
Another approach to removing quackgrass is known as solar sterilization, which uses heat to kill existing weeds. Take a clear piece of plastic the size of the weedy area and anchor it down with stakes directly over the area for five days. The heat buildup under the plastic will kill the vegetation. (This procedure also works well for removing creeping bentgrass, Agrostis palustris.) You can then reseed or re-sod the area. Remember to cut the plastic the exact size of the sod pieces you will use to replace the weed so no one will ever know that a weed once inhabited the spot ... just like the big leaguers!
Yellow Nutsedge
Also known as yellow nut-grass and ground almond, yellow nutsedge (Cyperus esculentus L.) spreads very rapidly and flaunts a distinctive yellow- to brown-colored flower and triangular stem. Pulling out the plant will not terminate this weed because long tubers underneath the soil are responsible for the spread of this plant. Yellow nutsedge thrives on water and is usually present in poorly-drained or over-watered areas. Fix any drainage issues or decrease water usage to prevent an onslaught of this weed.
To fight yellow nutsedge in cool-season grasses, apply halosulfuron (Manage®) or try Ortho® Weed-B-Gon® crabgrass control, as it contains MSMA, a postemergent herbicide effective on grassy weeds. You will need to repeat applications, so it is important to follow the directions rather than making a large single application. For warm-season grasses like bermudagrass and zoysiagrass, use the above mentioned products, or try imazaquin (Image®).
Torpedograss
Torpedograss (Panicum repens L.) mainly poses a problem to lawns in the southern coastal states. Found along ditches and ponds, torpedo grass boasts upright stems that reach two to three feet in height, as well as flat, folded leaves.
This weed spreads by rhizomes, making it extremely challenging to wipe out by hand pulling. To control this pest, you will need to repeat applications of quinclorac (Drive®).
Dallisgrass
Dallisgrass (paspalum dilatatum Poir.) is a perennial that is common in southern states where moisture is plentiful. This warm season grass grows in bunches with coarsely-textured leaves sprouting near its base. This plant also produces seedstalks that grow several feet above the ground.
If dallisgrass is marrying your lawn, put down dithiopyr (Dimension®) preemergent herbicide in the spring. Use MSMA/DSMA as a post emergent treatment or apply glyphosate using the paintbrush technique suggested above for quackgrass.
Identifying and controlling these problem weeds can be difficult, but by following these tips, you will be able to tackle those weeds that have kept you up at night. Some of the herbicides suggested for handling the top five "perennial pests" are not sold in garden stores, and can only be purchased through commercial applicators. But, this information will help you know your options for controlling these problem weeds, allowing you to suggest a solution to a professional (who may be searching for an answer as well).
