Lawn Burweed is a winter annual weed which grows rapidly in patches while turfgrass lawns are dormant (aggieturf.tamu.edu).
By: John Green, Certified Texas Expert Gardener, Orange, TX
Another cold snap (hopefully winter’s last) which has blanketed our area for several days requiring some of us (me included) to return sensitive plants to protected areas. Soon it will be time to return tropical plants outdoors but let’s wait a couple more weeks just to be certain the weather cooperates! It time to discuss lawn weeds again and how to control them!
Before delving into weed management, weed classification review is needed to provide the best way forward in managing and controlling weed populations. There are three weed classifications gardeners need to know: annual, biennial, and perennial.
An annual weed begins as a seed and completes its life cycle in under a year. They are 0ften easiest to control but the abundance of seeds produced at the end of makes them persistent year after year. Annual weeds can be further subdivided into summer and winter annual weeds.
Summer annual weeds germinate during spring, grow during summer and set seed in autumn. Seeds remain dormant through winter with the cycle repeating in spring. A few of the more common weeds in this category are cocklebur, morning glory, lambs’ quarters, common ragweed, crabgrass, pigweed, foxtail, and goose grass.
Winter annual weeds germinate in late summer (early autumn) with plants maturing to form seeds later in spring or early summer then dying. Their seeds stay dormant during summer’s heat which inhibits seed germination. A few common weeds to note are wild mustard, henbit, and spiny sowthistle.
Biennial weeds live longer than one year but less than two years and fortunately there are few weeds which fall into this category, such as: wild carrot, bull thistle, common mullein, and burdock.
Perennial weeds live two years or longer and are further subdivided by their reproductive process being simple or creeping.
Simple perennial weeds spread mostly by seed, but if cut into pieces, the segments can also propagate into new plants. An example is dandelion, when cut in half each piece it will produce a new plant! Other examples are buckhorn, plantain, broadleaf plantain, and pokeweed.
Creeping perennial weeds reproduce by roots that grow at or just below the soil surface using rhizomes but also produce seeds. Some of the weed’s roots grow deep into the soil, more than 12 inches deep, making complete extraction impossible as pulling the weed will leave roots or rhizomes in the soil which will allow the plant to regrow. Weeds such as red sorrel, perennial sow thistle, field bindweed, wild strawberry, mouseear chickweed, ground ivy, nutsedge (nutgrass), torpedo grass, smilax, Virginia buttonweed and quack grass are examples. Note these weeds are some of the hardest weeds to control!
The best line of defense to manage weeds is a well-established and healthy turfgrass. Many of us have St. Augustine grass for our lawn grass. Some yards have Bermuda grass, while others may have Centipede grass. Many lawns (mine included) have a mixture of turf grasses but are predominantly either Saint Augustine or Centipede. Maintaining a turfgrass lawn requires a good bit of time with lawn moving by far the most time-consuming activity for turfgrass maintenance.
Sharp mower blades are necessary to maintain a healthy and aesthetically pleasing lawn. Maintaining lawn equipment is necessary to ensure turfgrass health. The mower blades must be sharp, the mower deck height adjusted to remove the top one-third of turfgrass growth during each cutting.
The taller the grass blade height , the deeper the root structure. Fertilize the lawn with a slow-release fertilizer. Centipede grass does not like any type of weed & feed fertilizers, instead use a straight fertilizer mix (8-8-8 or 10-10-10). Allow turfgrass clippings to remain in place on the lawn as they will eventually decompose becoming mulch for the lawn. Watering is also an important practice in keeping a good turf root system growing. Lawns need an inch of water per week either via rain or an irrigation system. Deep watering is best especially when dry and is more efficient than shallow watering. Do not water to the point of runoff and always water when the wind is calm.
Pre-emergent herbicides must be applied before the weed seeds germinate and sprout through the soil surface. For control of warm-season annual weeds, apply pre-emergence herbicide in early spring (January to March), before the soil temperature reaches 55 degrees F. For weeds which tend to sprout later in the summer, a second application may be necessary in June or July. For cool-season annual weeds, apply in August to September.
HERBICIDES:
Post-emergent: are applied after weeds have sprouted. They are most effective when weeds are still small, less than 4 inches high.
Contact: cause damage wherever they touch a plant. For them to work well, they must cover all parts of the weed, i.e., leaves and stems, tops, and undersides.
Systemic: are absorbed via plants’ cell walls and then moved throughout the plant. They are applied to either the soil surrounding the plant, the plant itself or both. They are moved through the plant from foliage to roots, stems, or other parts of the plants. They work well on perennial weeds, as the herbicide moves into all parts of the plant, especially the root, tuber and rhizome which stops root growth. Must be applied multiple times in 6-to-8-week intervals especially true for tougher weeds.
Selective: will kill one type of plant but not others, like turf grasses. Non-selective herbicides kill almost any plant. Great care must be taken before using non-selective herbicides and they should be used as a last resort.
Texas A&M AgriLife Extension Service recommends the following treatments for these specific weed types which are prevalent in our area:
Sandbur, grassbur, spurweed, cocklebur: pre-emergent, apply by March 1; Brands – PreM by Lesco; Amaze Grass & Weed Preventor by Green Light; Surflan, A.S. by Southern Ag.; Weed & Grass Preventor by Lilly Miller; weed Stopper by Lawn & Garden Products.
Virginia Buttonweed: post-emergent in St. Augustine grass lawns, such as dicamba (Banvel) or products containing dicamba (Trimec) which provides some control with two or more applications in spring and summer. If some discoloration of St. Augustine grass can be tolerated, Confront at 2 pints per acre and Scotts DMC at 1 ounce per acre have demonstrated good control of buttonweed.
Crabgrass: several very good herbicides have been developed for turf as a result of that research. DCPA (Dacthal), simazine (Princep), besulide (Betasan, Pre-san), benefin (Balan), dithiopyr (Dimension), oxadiazon (Ronstar), oryzalin (Surflan), prodiamine (Barricade), pendimethalin (Pre-M) and napropamide (Devrinol) are some of the materials available for preemergence crabgrass control. Since crabgrass germinates from April to September in most areas of the country (slightly shorter periods in other areas), few of these herbicides provide season-long control. All these products should be applied about 2 weeks prior to the expected date of emergence of crabgrass
Dandelion: spray 2,4-D in spring before blooms set.
Chickweed: spray pre-emergent herbicides such as simazine, dithiopyr, dacthal, oryzalin, pendimethalin and isoxaben in fall.
Henbit: Dicamba, MCPP and 2,4-D demonstrated effective control in the fall and early spring.
Yellow Sorrel: apply in early spring pre-emergent herbicides such as dacthal, oryzalin (Surflan), pendimethalin (Pre-M), isoxaben (Gallery), dithiopyr (Dimension) and oxadiazon (Ronstar).
Prostrate or Spotted Spurge: dacthal, pendimethalin and Surflan have provided good pre-emergent control of spurge in warm season turfgrasses. To be effective, they must be applied in early spring with a second application being required 60 days after the initial application.
Quack grass and Torpedo grass: unfortunately, the only herbicide which will get rid of this weed is qlyphosate. Safe handling of this herbicide is critical! Wear gloves, long-sleeves, and a respirator (mask) when using this herbicide. Paint weed with brush to keep from damaging nearby plants. Or try to dig the plant out after it rains, making sure to get all the roots but note the roots can be a foot deep in the ground.
Nutsedge or nutgrass: pre-emergent herbicide metolachlor (Pennant) is labeled for the control of yellow nutsedge (commonly known as nutgrass) in ornamental beds. For post-emergent control of sedge, the herbicide imazaquin (Image) is labeled for purple and yellow nutsedge (commonly known as nutgrass).
Chamberbitter weed: pre-emergent herbicides with atrazine applied in the early spring prior to germination. Another found in granular form containing isoxaben must be watered in. Post-emergent herbicides also with atrazine are effective when applied to young weeds. Seeds need light to germinate so mulching with 3-4 inches in garden beds will help.
Please note the list of weeds is extensive, but these are the most common weeds in our area.
Until next time fellow gardeners, let’s go out and grow ourselves a greener and more sustainable world, one plant at a time! Please send your gardening questions to: jongreene57@gmail.com
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