Identifying and Controlling Grassy Weeds

To the untrained eye, distinguishing turf grass from grassy weeds is tough because the two can look identical. But with practice and persistence, you can learn to identify lawn weeds—and even the difference between grass and sedge—by inspecting the primary vegetative characteristics of your lawn.

Here are some of the features our TruGreen® experts use to weed out the bad grasses.

Crown. The white, thick part of the grass plant at soil level where the shoot meets the roots. It’s central to lawn health—if the crown dies, the grass plant dies.
Sheath. The lower (basal) portion of the grass leaf between the crown and the blade that encloses and protects young shoots of grass. Sheath margins may be split, split with overlapping margins or be closed.
Collar. The backside of a leaf where the blade and sheath join. Collars may be divided by a line that runs up the center (mid-rib) or be continuous. Collar shapes vary from narrow to broad and can have slanted or straight borders.
Blade. The section of the leaf above the collar. Characteristics to look for include the type of tip, roughness or smoothness, and mid-rib.
Vernation. The leaf arrangement of the youngest leaf (called the budleaf) and its surrounding sheath. Look to see if the budleaf is rolled or folded.
Ligule. A tip- or cylinder-shaped structure poking out from the top half of a leaf where the blade and the sheath join. Ligules can be membranous, hairy, both or absent altogether, making them useful for spotting grassy weeds in grass.
Auricle. A pair of appendages sticking out from the side of the grass leaf where the sheath and blade meet. Auricles can be short and stubby, large and claw-like, have short hairs attached or be absent, also making them useful grass identifiers.
Rhizomes. An underground stem that produces a new plant.
Stolons. A horizontal, above-ground stem that roots at the nodes (found in the crown) and gives rise to new grass plants.
Seed head. The flowering or seeding parts found at the top of the grass plant. Check if seed heads are spike or panicle to help with turf grass identification.

An essential part of identifying grassy weeds has to do with their life cycles. For example, you may be able to hand-pull a few annual weeds to enjoy a weed-free backyard cookout, but perennial grassy weeds have a deeper root structure that can give rise to new weeds—even if you no longer see the weeds in your lawn. Learn what the different life cycles of lawn weeds mean for your control plan.

Annual weeds. These weeds live for only one season and are typically easy to control because they lack the complex underground structures needed to spread new plant growth through creeping roots. Still, annuals produce tons of seeds that can infest and dominate your yard under the right conditions.

Summer annuals. These grass-like weeds begin to grow (germinate) in the spring, mature in the summer, and then produce seeds and die by the fall or first hard frost—an entire life cycle completed within 12 months.

Winter annuals. These weeds overlap two calendar years but last only 12 months total. They germinate and develop from late summer to early fall, remain semidormant during the winter and then flower in spring. Come late spring or early summer, they mature and die off as the weather warms.

Perennial weeds. Perennial grassy weeds can germinate and spread from seeds, but they also produce a root structure (tubers, bulbs or corms) that can birth new weeds from your lawn’s surface (using stolons) or from underground (using rhizomes).

Biennial weeds. These flowering plants generally live for two years. The first year consists of leaves, stems and root growth, followed by winter dormancy. In the second year, biennials flower and produce seeds, thus completing their life cycles.

Without a professional service, removing grass-like weeds without damaging your lawn is difficult. The biological similarities of turf grass and grassy weeds make both susceptible to control methods. For example, spraying crabgrass killer at the wrong time can kill your grass seeds. Instead, aim to control grassy weeds by keeping your lawn dense and healthy so they don’t stand a chance. If these turf grass imposters have already invaded your lawn, you can try a few other tactics to weed them out.

What’s the Best Weed Control?

The most effective weed control is a flourishing lawn because it’s more competitive and will crowd out grassy weeds. Weed seeds need light to grow, which a dense lawn blocks out. To keep your lawn lush, healthy and competitive, try:

Fertilization. The right type and application method makes all the difference.
Mowing. Mow frequently at the recommended height with sharpened blades, removing only one-third of the leaf blade.
Watering. Water deeper rather than more frequently when rainfall is scarce.
Changing. Factor in climate, sunlight, shade, etc., to pick the right turf grass. [Links to J.5 Turf Grass Selection Module]

Does Pulling Weeds Work?

Hand-pulling grassy weeds can work if there are only a few, especially if they’re annuals. Perennial grassy weeds are harder to control by hand because you don’t always pull up the vegetative structure, which is what sprouts new weeds.

What Type of Crabgrass Killer Won’t Harm My Lawn?

Postemergence herbicides control existing weeds. Unfortunately, because grassy weeds are in the same family as turf grass, these types of herbicides can also harm your lawn. Preemergence herbicides control seeds only—not existing weeds—making them safer for an established lawn (grass seeds are susceptible). They work on most seed-based annuals and perennials.

Because each yard is unique, TruGreen® customizes a grassy weed control program for your lawn. The plan of attack depends on your region, type of turf grass and the specific weeds invading your lawn.

Grassy Weeds

Identify

Life Cycle

Control

Grow Your Knowledge With Lawn Care 101

Grow Your Knowledge With Lawn Care 101