Crabgrass vs Dallisgrass vs Quackgrass: How To Tell The Difference

Although it’s trying to pose as turfgrass, you know better. What is that pesky nuisance weed, standing out like a sore thumb in your lawn? Is it crabgrass? Is it dallisgrass? Or is it quackgrass? How do you tell the difference?

The first step in ridding your turf of unwanted grasses is determining exactly what species are growing in your lawn. So, let’s talk about how to tell the difference between crabgrass, dallisgrass, and quackgrass.

Crabgrass (Digitaria ischaemum and Digitaria sanguinalis) is native to Europe or Eurasia and is now found worldwide in temperature climates.

Technically an annual weed but it grows like a perennial because of its prolific self-seeding.
Shallow crab-shaped root system.
Young seedlings resemble a tiny corn plant.
Leaf blades are ⅖ to ½” wide.
Blades are a lighter shade of green and have a slight shine.
Reddish hue near the base of the stems.
Leaf blades can be covered in hairs or smooth, depending upon species.
Leaf sheaths angle out from the stem to grow in a star pattern.
Seedlings develop side shoots that eventually grow as individual branches.
Seedheads are small and delicate, with an abundance of seeds.
Grows incessantly to form a dense mat within the turf.
Crowded out by thick, healthy grass.
Thrives in hot, dry weather.

Dallisgrass (Paspalum dilatatum) is native to Central and South America. It is now found worldwide in tropical, subtropical, and temperate zones.

Cool-season perennial weed.
Blades have a coarse texture.
Leaf blades are a darker shade of green with a matte type sheen.
Blades are ¼ to ½-inch wide.
Plants grow rapidly in a more upright, vertical fashion.
Seedheads grow off the sides of the stems.
Seedheads are more prominent in size and have small black spots.
Develops short rhizomes for reproduction.
Forms an ever-enlarging circular clump as it grows.
Proliferates in dense, healthy turf that is heavily fertilized with nitrogen.
Adapted to thrive in both wet and dry weather.

Quackgrass (Elymus repens) is native to Europe. It is now mainly found in temperate regions in the Northern hemisphere and higher altitudes in warmer climates.

Cool-season perennial weed.
Blades are ashy-blue green in color and have a dull sheen.
Blades are ¼ to ½-inch wide.
Rhizomes grow deeply into the soil.
Stems grow singly instead of in clumps or mats.
Thick, coarse leaves with auricles that wrap around the stem.
Hairless stems and leaf sheaths.

Does Crabgrass Killer Also Kill Dallisgrass & Quackgrass?

Dallisgrass and quackgrass are commonly found weeds in lawns. Dallisgrass was first introduced in the 1880’s as a forage for livestock and grows aggressively in circular patches.

A lover of nitrogen, fertilizers encourage the growth of dallisgrass, especially in sandy or clay soils when it is well suited.

Quackgrass is similarly aggressive and will release chemicals that inhibit the growth of other plants. Unlike crabgrass which it is commonly mistaken for, quackgrass has a very deep root system.

Typically, preemergent herbicides that are used to combat crabgrass are effective tools against dallisgrass. Less robust than crabgrass, dallisgrass is easily handled by preemergent chemicals.

The preemergent will prevent seed growth as long as it is watered into the ground thoroughly. As with preemergent, any post emergent that is effective against crabgrass will also be effective in the control of dallisgrass.

Numerous treatments over the course of several weeks may be required to totally eradicate the outbreak. Small outcroppings can also be treated with nonselective herbicides although care must be taken to ensure it does not kill any desirable plants.

Quackgrass is more challenging to control. Although it is commonly confused with crabgrass, quackgrass is not generally effected by crabgrass killer and usually requires the use of a nonselective herbicide to control.

Because quackgrass relies very heavily on food stored in its root system, frequent treatments are required to completely kill of the weed. Frequent mowing will help to prevent quackgrass from continuing to grow because its ability make food will be impaired.

Unfortunately, there is no effective chemical preemergent care for quackgrass, because it does not germinate from seeds but a rhizome (underground stem). The best preemergent treatment for quackgrass is a strong, thick lawn that prohibits initial growth. Once growth occurs however, options are limited to digging out the quackgrass (it is very difficult to ensure the entire root system is removed) or by the application of a nonselective herbicide.

Growth of quackgrass occurs in the spring and fall months so dormancy in the summer is normal. The best prevention for a quackgrass outbreak is good lawn management prior.