Dallisgrass Vs. Crabgrass

Often, we make costly mistakes without knowing the future consequences. A. T Dallit backed the use of Dallisgrass as a forage crop. The imported grass turned out to be a nuisance. Don’t make the same mistake as a homeowner and allow Dallisgrass or crabgrass on your lawn. They are invasive and could make your lawn unsightly. 

While crabgrass might encroach on your lawn every year, dallisgrass poses a threat to your cattle due to its vulnerability to ergot fungus. Dallisgrass has a large seedhead with tiny black spots which grow off the stems from different points, while crabgrass has a fine small seedhead that cuts out from the top of the stem.

Dallisgrass and crabgrass are prevalent warm-season weeds. They look almost similar when mature, so people often mistake one for the other. The main structural difference between dallisgrass and crabgrass is the seedhead.

Here are distinguishing features to identify and know the best corrective measures to remove them. 

What is dallisgrass?

Dallisgrass (Paspalum dilatatum) is a fast, vertically growing perennial weed with a bunch type growth habit. It grows tall and can reach approximately 5 feet if left uncut.

The rhizomes of dallisgrass are short and grow fast to spread the weed over the lawn to form a circular, stiff, and thick clump. Dallisgrass grows fast. The short rhizomes that grow yearly are challenging to control once they have invaded your lawn. Furthermore, the pesky weed escapes a reel mower.

The leaves of dallisgrass are coarse-textured, dark green, and dull. It’s hairy on the leaf collar and, in some instances, the leaf blades’ base.

Dallisgrass’ main identifying feature is the seedhead. The large seedhead has tiny black spots and grows from different points of the stems’ sides.

Dallisgrass has thick, deep fibrous roots with ridges.

What is crabgrass?

Crabgrass (Digitaria spp) is a fast-growing annual weed established from seeds on the lawn in early summer.

Crabgrass lacks short rhizomes. It spreads by new shoots that develop from the side branches of the stem to form a thick mat of weeds resembling a star.

The fine small seedhead of crabgrass grows out from the top of the stem. Its seedlings resemble a corn plant.

Each variation of crabgrass weed has different leaf blades. The leaf blades’ variation enables each weed to survive in different environments. The two main varieties are the large or hairy crabgrass and the small or smooth crabgrass. While large crabgrass has hairs on the leaf blades, smooth crabgrass has few or no hairs.

Overall, the leaf blades of crabgrass are lighter green, shiny, and 1/4 to 1/3 inch broader than dallisgrass leaf blades. The blades are further and angle out from the stem. The seedling develops side shoots that grow as separate stems or branches.

Dallisgrass vs crabgrass: differences

Dallisgrass and crabgrass thrive in the warm summer months and compete with weeds for space and nutrients. While they may look similar, look at these distinctive features to tell them apart. 

  • Life cycle
  • Seedhead arrangement
  • How they appear
  • Leaf morphology
  • How they establish and spread
  • Ease or difficulty of removing them from the lawn

The table below summarizes the significant differences between dallisgrass and crabgrass.

DallisgrassCrabgrass
Perennial weedSummer annual weed
Large seedheads which cut from different spots on the stemFine, small seedhead that cuts out from the top of the stem
Coarse-textured leaf bladesFine or coarse-textured leaf blades
Dark green, narrow leavesLight green broad leaves
Establishes and spreads by short rhizomesEstablishes and spreads by seeds
Difficult to controlLess difficult to control

Life cycle

Dallisgrass is a perennial weed, while crabgrass is an annual summer weed.

Dallisgrass grows back to the lawn after each year. It establishes from the grown underground fast-spreading shoots called rhizomes. The rhizomes develop and send new shoots that grow above the ground in early summer.

On the other hand, crabgrass has a short lifespan of one year. Crabgrass seeds start germinating in late spring or early summer in favorable conditions. The weed thrives throughout summer and reproduces sources left on the lawn. Wind, birds, and animals later spread the seeds. Crabgrass dies in the first fall frost, leaving its seeds to establish in the following season.

Seedhead arrangement

Dallisgrass has large seedheads, while crabgrass has fine, small seedheads.

Dallisgrass seedlings grow from the sides of the stem. Their large size makes them easily identifiable. Furthermore, they have small black spots that tell them apart from crabgrass. 

Conversely, crabgrass has fine and small seedheads with no black spots. The seedheads cut out from the top of the stem.

Appearance

Dallisgrass forms circular clumps on the lawn, while crabgrass forms a reminiscent star of shoots.

Dallisgrass forms a thick, stiffer circular clump of shoots. The underground rhizomes have a wide diameter from which new shoots develop and spread fast to form circular clumps.

On the other hand, crabgrass forms a thick mat, with numerous side branches emerging to resemble a star.

Leaf morphology

Dallisgrass has dark green leaves, while crabgrass leaves are a lighter shade of green..

The leaf blades of dallisgrass are coarse-textured and have a dull surface.

Meanwhile, the leaf blades of crabgrass are light green and they can have a smooth or rough texture depending on the type. They are also shiny on their surfaces.

If they were growing in the same space, you could identify dallisgrass by its narrow leaves. Crabgrass has broad leaves, which might explain how they cover expansive areas in a short time. 

How they establish and spread

Dallisgrass establishes and spreads by its short rhizomes, while crabgrass establishes and spreads by seeds.

In early summer, Dallisgrass develops new shoots from the short underground rhizomes. The rhizomes expand their diameter and grow new shoots throughout summer.

On the other hand, crabgrass establishes from the dormant seeds produced from the previous growing season. Animals, winds, and water spread the seeds over the lawn. The seeds germinate and sprout to seedlings and thrive throughout the summer months. While actively growing, the plant produces more seeds that grow and spread in the following season.

Ease of control

Dallisgrass is more challenging to control, while crabgrass is easier to control.

Dallisgrass is a perennial weed and stays for years before ending its life cycle, once established in a lawn. It regrows every year from the short rhizomes that develop new shoots in the growing season. The roots store carbohydrates and keep supplying the plant with food to regrow. This makes it difficult to remove the weed once established.

If you kill their seeds with pre-emergent herbicides but leave the rhizomes, they would regrow. The best control measure to keep dallisgrass from your lawn is identifying it while young before the rhizomes establish and dig the whole plant. Using post-emergent herbicides requires multiple applications.

On the other hand, crabgrass is easier to remove from the lawn as it is an annual weed that thrives in one growing season and dies in the first fall frost. The best method to control the weed is by applying preemergent herbicides in late spring to kill their seeds, preventing them from germinating. Make a second application to kill the remaining seeds. Crabgrass doesn’t have indigenous rhizomes to regrow yearly like dallisgrass, thus proving easier to remove from the lawn than dallisgrass.

References

  1. University of Maryland Extension: Dallisgrass.
  2. University of Minnesota Extension: Tips for controlling crabgrass in your lawn.

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