Virginia buttonweed (Diodia virginiana) is a common weed encountered by most gardeners. It appears quickly and grows rapidly in SETX landscapes. Many ornamental plants and lawns are initially surrounded, then engulfed by the prolific weed. Most gardeners consider it to be a major nuisance and cumbersome to control (image courtesy: advancedturf.com).
by John Green, Texas Certified Expert Gardener
Last week I discussed struggles gardeners face to manage weeds from overtaking flower beds, vegetable gardens, and landscapes this time of year while attempting to do so without harsh chemicals-utilizing organic methods which in my experience have proven to be successful. The methods discussed are best suited for use in flowers beds and vegetable gardens, but a few readers submitted questions asking about how to control weeds in lawns?
Simply put, managing weeds is a struggle most of us face, especially during the summer season. We are experiencing a summer with more rainfall than typical (this gardener is whole-heartedly grateful), yet there are consequences for the abundant supply of moisture accompanied by elevated temperatures in our nutrient rich environment-it’s the perfect growing situation for most ornamental plants, crops, lawns, and unfortunately summer weeds!
As most readers understand, my preference is to “always” use the least environmentally impactful method to provide plant nutrition and control weed populations…but there are times when more drastic measures are warranted. If weeds are gaining the upper hand, more stringent control methods might be necessary. It is important to know the enemy (weed variety) before utilizing non-organic control measures. It is also critically important to know the turfgrass variety (predominatetype in the lawn), as some herbicides can damage some varieties of turfgrass. Understanding the consequences of applyingselective spectrum (not broad spectrum) herbicides or not following manufacturers herbicide application directions exactlywill negatively impact our environment with significant detrimental effects to pollinators and wildlife. Be mindful before using herbicides, and only use them as a last resort!
Weed populations are exploding everywhere with exponential growth. Maintaining lawns, gardens, and landscape are encumbered due to the amount of rainfall which makes it difficult for many of us to mow lawns or remove weeds, meaning the weeds are gaining a stronghold – (winning) for the moment! Frequent lawn maintenance typically keeps weeds from gaining a strong foothold. Selecting a mower deck height between 1.5 to 3-inches (depending on lawn grass variety) allows the lawn to grow optimally which most often will “crowd” weeds out of existence by outcompeting the weeds for available nutrient and moisture resources.
Weeds, Weeds and More Weeds (Two Most Common Varieties)
Virginia buttonweed– is a warm season perennial weed that thrives in heavy clay soil which is poorly drained. They are low growing weeds which spread underground through rhizomes and by seeds. The shiny leaves are small, oval-shaped structures protruding from square shaped stems, displaying abundant small white flowers blooming from June through October. The plant forms dense mats beginning in late spring to early summer. The weed competes with turfgrass for nutrients and moisture, especially problematic in Bermuda and St. Augustine grasswhere it survives mowing, quickly regrowing. The key to control Virginia Buttonweed is maintaining lawn health: adequate fertilization (not excessive) and moisture with frequent lawn maintenance- are basic control strategies. Physically removing small patches of Virginia buttonweed is easy and larger areas can be “carefully” treated with selective herbicides such as metsulfuron methyl. If herbicides are necessary to control, apply during the summer season while weed is actively growing. Metsulfuron methyl can be safely applied on St. Augustine, Centipede, Bermuda, and Zoysia grass during the summer season. This type of herbicide requires repeated applications at 4 to 6- week intervals.
Note: Carpet grass can be damaged and Bahia grass will be killed by metsulfuron methyl exposure.
Torpedo grass– is a perennial grass which is a problem in SETX. There are few lawn problems which are more devastating than a torpedo grass infestation. Torpedo grass is extremely tolerant of most herbicides, outcompeting slower growinggrasses, such as centipede. Unfortunately, torpedo grass spreads quickly across the landscape but some lawn types can suppress torpedo grass depending on the turfgrass species. Selectively removing torpedo grass from lawns is often not successful, due to the anatomy of the grass. Quinclorac is an herbicide which is somewhat effective in suppressing torpedo grass in Bermuda and zoysia grass.
Note: Centipede and St. Augustine grass will not tolerate this herbicide and will be severely damaged.
Another herbicide, sethoxydim will temporarily ‘knock down’torpedo grass infesting centipede grass, though it does not provide long-term control and torpedo grass will recover.
Unfortunately, there are no selective herbicide options for torpedo grass infesting St. Augustine grass. According to Ron Strahan (Weed Scientist and Turfgrass Specialist-LSU) states “often a complete renovation is necessary when centipede or St. Augustine grass are severely infested. If you decide to renovate and install a new lawn, consider sodding the lawn with zoysia (semi-shady or full-sun lawns) or Bermuda grass (for full sun only)”.
Proper lawn maintenance can aid gardeners in keeping weeds at bay…weather permitting! There are many more weeds we can discuss, a subject for a later date. So long for now fellow gardeners! Let’s go out and grow ourselves a greener, more sustainable world, one plant at a time! Thank you for the questions & kind comments. Please continue sending gardening questions to: jongreene57gmail.com.
Social Media