Few lawn problems cause as much confusion as grassy weeds.

Crabgrass, Dallisgrass, Goosegrass and even Bermudagrass can look surprisingly similar at certain stages of growth, yet the way we prevent and treat each one can be very different.

Our goal with this guide is to simplify a confusing subject and help you understand where these weeds come from, why they appear, how to identify them and what you can do about them.

Where Do All These Weeds Come From?

One of the first questions we hear is, “Where did these weeds come from?”

The truth is, weed seeds are virtually everywhere. Soil can contain thousands of dormant weed seeds in a relatively small area. Heavy weed infestations certainly lead to additional seed production, but the presence of weed seed alone does not mean you will have a weed problem. What usually makes the difference is the environment surrounding that seed. A weed needs an opening and the right growing conditions to become established. Thin turf, bare soil, excessive moisture, drought stress, compaction, improper mowing and other environmental stresses can all create opportunities for weeds to germinate and grow. That is why good weed control begins with more than simply reaching for a weed killer.

A Healthy Lawn is Your First Defense

A thick, actively growing lawn leaves less room for weeds to become established. Before focusing only on herbicides, pay attention to the conditions of the lawn itself. Important steps include:

• Keep the lawn properly fertilized throughout the growing season.
• Mow cool-season fescue lawns at approximately 3–4 inches high.
• Avoid scalping the lawn or trimming edges excessively short.
• Keep mower blades sharp to reduce stress and disease pressure.
• Manage drought stress whenever possible.
• Reduce soil compaction and excessive traffic.
• If you have automatic irrigation, avoid overwatering.
• Correct thin or bare areas where weeds can easily become established.

The healthier and denser your lawn becomes, the less opportunity weeds have to take over.

Understanding Weed-Control Products

Once good lawn practices are in place, herbicides can become another important part of weed management. There are several different categories, and understanding the difference is important.

Pre-Emergent Herbicides

Pre-emergents are one of our most valuable tools for preventing annual & perennial grassy weeds. The key word is prevention.

After application and proper watering, the herbicide forms a treated zone near the soil surface. When a susceptible weed seed begins to germinate, the young root or shoot contacts that treated area and development is stopped. Pre-emergents work best before annual weeds such as Crabgrass and Goosegrass become established. Once those weeds are mature and actively growing, a pre-emergent will not kill the existing plant.

In seasons with extended rainfall and a long germination period, a second properly timed application is almost always beneficial. Always follow the product label regarding application timing and reapplication intervals.

Selective Post-Emergent Herbicides

A post-emergent herbicide is applied after a weed has already begun growing. A selective post-emergent herbicide is designed to control certain weeds without permanently damaging certain desirable turfgrasses when it is used according to the label. The important word here is selective. A product that is safe for one type of lawn may damage another, so knowing both your weed and your lawn type is essential. (Example: typically, we have fescue lawns in the South but more developers are incorporating Zoysia/bermuda type grasses into new builds. Some herbicides will damage those lawns)

Non-Selective Herbicides

A non-selective herbicide is intended to kill or severely damage most vegetation it contacts. Glyphosate-based products, including products such as Hi-Yield Killzall, are common examples. These products can be useful for spot treatments in certain landscape areas or when completely renovating an area, but extreme care should be taken around desirable turf, flowers, shrubs, perennials and groundcovers.

Weed Suppressants

Some herbicides can be used to suppress a difficult weed without harming the desirable lawn. One example is Hi-Yield Triclopyr Ester, which may be used in certain cool-season turf situations to help suppress Bermudagrass and other tough weeds like Ground Ivy when applied according to label directions. Suppression is different from eradication. Multiple treatments may be necessary, and using a stronger-than-labeled mixture in an attempt to get faster results can also injure the desirable turf. Always follow the herbicide label.

Annual vs. Perennial Grassy Weeds

This distinction explains why some weeds seem relatively easy to stop while others return year after year.

Annual Grassy Weeds

Annual weeds complete their life cycle in one season and return primarily from seed. This makes pre-emergent control extremely important, because preventing the seeds from successfully germinating can break much of the cycle.

Examples include:

• Crabgrass
• Goosegrass

Perennial Grassy Weeds

Perennial weeds can return from established roots, crowns, rhizomes or other underground structures in addition to producing seed. That makes them considerably more difficult to control.

Examples include:

• Dallisgrass
• Bermudagrass
• Nutsedge, although technically a sedge rather than a grass

Identifying Our Most Common Grassy Weed Problems

Crabgrass

Type: Annual

Crabgrass is one of the most common grassy weeds in stressed or thinning lawns. It thrives where turf is weak and is often especially aggressive in compacted areas. As it grows, Crabgrass develops a low, spreading growth habit that can quickly fill open areas.

Best Control Strategy Selective post-emergent products are available for Crabgrass, but they are generally most effective while plants are still young and actively establishing. The biggest emphasis should be on properly timed pre-emergent applications.

During long, wet springs or summers, Crabgrass may continue germinating over an extended period, making proper pre-emergent timing and coverage even more important.

Dallisgrass

Type: Perennial

Dallisgrass is one of our more difficult grassy weeds to manage. It commonly grows as a coarse clump, although heavy infestations can eventually form large patches throughout a lawn. One of its easiest identifying characteristics is the tall seed stalk. Several seed branches extend from the stem at an angle and can become very noticeable only a few days after mowing.

Best Control Strategy

Because Dallisgrass is perennial, established plants can return from their root systems year after year. Pre-emergents can help reduce new plants developing from seed, but they will not eliminate established clumps. Control of existing plants can be difficult. Carefully targeted applications of a non-selective herbicide may sometimes be used, but protecting the surrounding desirable lawn is extremely important. Prevention, early identification and persistence are key.

Goosegrass

Type: Annual

Goosegrass is another annual grassy weed that favors thin, compacted and stressed areas. It is generally not as aggressive as Crabgrass or Dallisgrass, but it can still become a noticeable problem where lawn conditions allow it to establish.

Best Control Strategy

Pre-emergent herbicides are an important preventive tool. Selective post-emergent products may also be available, with control generally being easier when plants are young rather than fully mature.

Nutsedge or “Nut Grass”

Type: Perennial sedge

Although many people call it “Nut Grass,” Nutsedge is technically not a grass at all. It is a sedge. Several different types of Nutsedge occur in our area. It is often most noticeable during periods of abundant moisture and may become especially active during wet spring and fall weather or following periods of heavy summer rainfall. Nutsedge can spread through underground structures, including small tubers, which help it return after the visible foliage has been removed.

Best Control Strategy

Selective products are available for controlling Nutsedge in certain lawns and landscape situations. Because of its underground structures, significant infestations may require repeated treatments over more than one season. Pulling can remove the visible plant, but if underground portions remain, new growth may return. Sedge Ender can be used for control of Nutsedge in the lawn.

Bermudagrass

Bermudagrass creates a unique problem because it isn’t technically a weed species at all.

In warmer Southern climates, Bermuda is intentionally grown as a desirable lawn grass. In fact, there are neighborhoods in our area that developers use a type of Bermudagrass as a lawn grass. In a cool-season fescue lawn or landscape bed, however, it can become an extremely aggressive unwanted plant.

Bermuda spreads through both:

• Stolons — runners that travel across the soil surface
• Rhizomes — runners that travel below the soil surface

These runners allow Bermuda to move aggressively between neighboring lawns, beds and landscape areas. Bermuda also goes dormant during cooler weather, turning brown for from roughly late October through March before becoming active again as temperatures rise. Its long spreading runners sometimes cause it to be mistaken for Crabgrass. The foliage is finer than Crabgrass.

Why Pre-Emergent Doesn’t Solve Bermuda

Unlike an annual grassy weed such as Crabgrass, established Bermuda isn’t returning primarily from new seed each year. It is spreading from its existing stolons and rhizomes. For that reason, a traditional pre-emergent program alone will not eliminate established Bermudagrass.

Best Control Strategy

Where appropriate in landscape areas, non-selective herbicides can be used to treat Bermuda. Heavy infestations may require repeated treatments because of the amount of living material below the soil. In fescue lawns, certain herbicides may be used to suppress Bermuda while minimizing permanent injury to the desirable fescue when used exactly as directed. Suppression should not be confused with complete eradication. Bermudagrass is one of the most persistent lawn invaders we encounter. Triclopyr Ester can be used to suppress Bermuda in the lawn or landscape but follow direction labels and apply accordingly.

What About Grassy Weeds in Landscape Beds?

Grassy weeds don’t stop at the edge of the lawn. They can also spread into mulched beds, gravel areas, perennial gardens, groundcovers and other landscaped spaces. In open mulch or gravel areas, controlling grassy weeds may be easier because there are more opportunities for carefully targeted spot treatments because there are more opportunities for careful targeting spot treatments with non-selective herbicides such as Hi-Yield Killz-All. Problems become more complicated when weeds grow directly through flowers, perennials, groundcovers or other desirable plants. In these situations, the same challenge found in a lawn applies: we want to remove one plant without damaging another. Correct identification becomes especially important before applying any herbicide.

What If I Don’t Want to Use Herbicides?

Some alternative and organic weed-control products are available, although their effectiveness, cost and number of applications required may differ from conventional herbicides.

For homeowners who choose not to use herbicides, greater emphasis should be placed on:

• Maintaining dense, healthy turf.
• Proper mowing.
• Improving soil and growing conditions.
• Reducing compaction and stress.
• Manual removal.
• Preventing weeds from producing additional seed.
• Accepting some level of weed presence where complete control isn’t practical.

No matter which approach you choose, changing the conditions that allowed the weed to become established is an important part of long-term control.

Identify First. Treat Second.

This may be the single most important takeaway.

Don’t assume every spreading grassy weed is Crabgrass.

Crabgrass, Dallisgrass and Bermudagrass may look similar to an untrained eye, but their life cycles and treatment options are very different.

Before choosing a weed-control product, determine:

1. What weed do I have?
2. Is it annual or perennial?
3. What type of lawn or desirable plants surround it?
4. Am I trying to prevent, suppress or eliminate it?

Once those questions are answered, choosing the right approach becomes much easier.

Not sure what is growing in your lawn? Bring us a fresh sample or several clear photos. We can help you identify the problem and determine which control options are appropriate for your lawn or landscape.

Correct identification, good lawn management and properly timed treatments will always produce better results than simply spraying first and hoping for the best.

Consider our 4 Step Lawn Care for year round fertilization and weed control in your lawn.