MASTER GARDENER — Conquer weeds by knowing YOUR foe
Published 12:02 am Wednesday, April 5, 2023
Let’s discuss turfgrass weed management. Before you start rolling your eyes, and thinking to yourself, blah, blah, blah…boring, just know that beautiful, healthy, weed-free and well-manicured lawns don’t occur by accident.
They require each of us to learn about and understand specifics about the turf grasses in our lawn, types of weeds present, and creating a systematic approach to maintain a healthy, weed-free lawn, in an environmentally friendly way.
When performed correctly, lawn weed control doesn’t require much effort, but it does require being informed. So, before discussing weed management, we need to understand the basics, as there are three fundamental groups of weeds: annual, biennial and perennial.
This is the first step in developing a strategy to effectively manage weeds, since each group is managed differently.
Annual weeds germinate and complete their life cycle in under a year and are often easiest to control but due to the abundance of seeds produced at the end of their life cycle, can become persistent. Annual weeds are sub-divided into summer and winter annual weed groups.
Summer annual weeds germinate in spring, and grow during summer and flower, setting seeds in fall. Seeds remain dormant through winter, germinating the following spring, beginning the cycle again. Summer annual weeds include cocklebur, morning glory, lambs quarters, common ragweed, crabgrass, pigweed, foxtail and goose grass.
Winter annual weeds germinate in late summer, fall and winter, where plants mature forming seeds in spring or early summer completing their lifecycle. Summer’s high temperatures inhibit seed germination. This group includes wild mustard, henbit and sow thistle.
Biennial weeds live more than one year and less than two. There are but a few weeds in this category, such as wild carrot, bull thistle, common mullein, and burdock.
Perennial weeds live two years or longer. They are grouped by method of reproduction: simple or creeping.
Simple perennial weeds generally spread by seeds but if cut, their pieces can produce new plants. For example, if dandelion is cut in half each, each half will produce new plants, creating two plants. Other examples are buckhorn, plantain, broadleaf plantain and pokeweed.
Creeping perennial weeds reproduce by their roots creeping along the soil surface or beneath the soil with rhizomes, in addition to seeds. Examples are red sorrel, perennial sow thistle, field bindweed, wild strawberry, mouse ear, chickweed, ground ivy, nutsedge (nutgrass), torpedo grass, smilax, Virginia button weed and quack grass.
Once your lawn has become infested with weeds, know that some of the listed weeds are difficult to control, since many of them have roots and rhizomes which grow deeply into the soil, some a foot or more.
Pulling the weed most often leaves roots and rhizomes in the soil, allowing the plant to regrow, doubling the amount of weeds present. The best defense against weeds starts with a well-established turfgrass lawn.
The vast majority of SETX lawns are St. Augustine grass, followed by Bermuda grass in some and Centipede in others. Our lawn, like many of yours, has a mix of turfgrasses, St. Augustine and Centipede. Turfgrass maintenance requires an investment of time and energy.
Let’s face it, lawn mowing is time-consuming but necessary to maintain the lawn’s health. Sharpen the mower blades and set the mower deck height so that no more than one third of the growth per cutting is removed. The taller the grass, the deeper the root structure!
Fertilize using a slow-release fertilizer, as this will make for a nicer looking lawn, and note that Centipede grass does not like weed and feed fertilizers, but rather needs a straight fertilizer mix such as 8-8-8. Grass clippings are a gift of mowing, so just leave them in place after mowing.
I know for some of you this is difficult because ‘they appear unsightly’, get over it already…it’s a momentary thing. The clippings dry quickly and filter down to the turf grass roots helping to retain moisture, cool root structure, provide nitrogen back into the soil as they decompose, reducing the amount of fertilizer required. Watering the lawn is an important practice in keeping a good turfgrass root system growing and deeply watering the lawn is better and more efficient than shallow watering.
Weed control can be achieved through diligence, in a couple of ways: manually (most environmentally friendly) digging weeds individually which isn’t an issue if there are but a few in your landscape, though more exhausting and labor-intensive for large areas.
For large areas infested by weeds and without Turfgrass, covering the area with plastic for around 4 weeks, allowing the sun to do the ‘heavy lifting’ by cooking the weeds.
Organically (environmentally friendly) or chemically, by using pre and post emergent herbicides.
Pre-emergent herbicides are applied before the weeds sprout and to control warm-season annual weeds, apply pre-emergent herbicides in early spring (January to March), before the soil temperature reaches 55 degrees F. For weeds which sprout later in summer, a second application is necessary in June or July and for cool-season annuals, August to September.
Post-emergent herbicides are applied after weeds have sprouted and are most effective when weed seedlings are less than 4 inches tall.
Contact herbicides destroy cell tissue wherever they touch a plant and for them to work well and must cover all plant parts leaves, stems, tops and undersides.
Systemic herbicides are absorbed, moving throughout the plant. They can be applied to the soil at the plant’s base, the plant itself or both. They are moved thru the plant foliage, roots, stems or other parts working particularly well by killing the root, tuber, and rhizome growth. These herbicides must be applied at 6-to-8-week intervals, especially when dealing with more cumbersome weeds.
Selective herbicides eradicate one type of plant, leaving others unaffected, like turf grasses.
Nonselective herbicides destroy all plants. Great care must be taken before using this type of herbicide and should be used as a last resort! As with all herbicides, it is imperative to always read the directions for use before applying to make certain the product will specifically control the problem weed, so please read before spraying!
John Green is Texas Certified Master Gardener with Orange County Master Gardeners. To have gardening questions answered in detail, contact him at email@example.com, reach out to Orange County Master Gardeners Helpline at 409-882-7010 or visit https://txmg.org/orange, Facebook: Orange County Texas Master Gardeners Association or by email firstname.lastname@example.org.