Dallisgrass vs Crabgrass: Weed Identification, Control, and Key Differences

Keeping a lawn healthy and weed-free can feel like a full-time project—especially when aggressive grasses like Dallisgrass and Crabgrass start taking over. Although many homeowners confuse these two weeds, they differ significantly in structure, growth habits, control methods, and long-term management strategies.

Understanding the differences between crabgrass and dallisgrass is essential for choosing the right treatment and preventing reinfestation. In this in-depth guide, we’ll break down how to identify them, why they invade lawns, and the best ways to get rid of each.

🌱 What Is Crabgrass?

Crabgrass is an annual warm-season weed—which means it completes its life cycle within one year. It grows aggressively during summer, produces thousands of seeds, and dies in fall when temperatures cool.

✔ Scientific Name:

• Smooth Crabgrass: Digitaria ischaemum
• Large Crabgrass: Digitaria sanguinalis

✔ Growth Behavior:

• Germinates when soil temperatures hit 55°F–60°F (12°C–16°C)
• Thrives in heat, full sun, and dry compacted soil
• Dies completely each winter
• Returns through new seeds every spring

✔ Seed Production:

A single crabgrass plant can produce 100,000+ seeds, making it extremely persistent.

🌾 What Is Dallisgrass?

Dallisgrass is a perennial warm-season weed, meaning it returns year after year and survives winter through an underground root system (rhizomes).

✔ Scientific Name:

• Paspalum dilatatum

✔ Growth Behavior:

• Grows in clumps (“crowns”)
• Spreads through both seeds and underground rhizomes
• Prefers moist soil, full sun, and fertile conditions
• Very difficult to eradicate because roots remain alive

✔ Lifespan:

It does not die in winter, only goes dormant, then regrows in spring.

🟩 Dallisgrass vs Crabgrass: Quick Comparison Chart

🌱 How to Identify Crabgrass

Crabgrass typically appears in mid-to-late spring, especially in weakened areas of the lawn. Recognizing it early helps prevent spreading.

✔ Appearance

• Low-growing and spreads outward
• Forms a mat-like shape resembling a crab (hence the name)
• Leaves are light green and smooth
• Young plants look flat; mature ones appear star-shaped

✔ Growth Style

• Stems radiate horizontally
• Nodes root into soil wherever they touch
• Very shallow root system
• Prefers heat and poor soil

✔ Seed Heads

• Long, thin, finger-like seed heads
• Usually 3–5 spikes per stem
• Rises above the leaf canopy in late summer

✔ Seasonal Pattern

• Germinates: Early Spring
• Thrives: Summer
• Seeds: Late Summer–Fall
• Dies: First frost

When winter hits, crabgrass disappears completely—but the seed bank remains.

🌾 How to Identify Dallisgrass

Dallisgrass is easy to confuse with crabgrass early in the season, but certain characteristics make it distinct.

✔ Appearance

• Grows in large, tough clumps
• Leaves are coarse, wide, and bluish-green
• Resembles a thick, unruly bunch of tall grass

✔ Growth Style

• Center “crown” thickens over years
• Grows upright, not outward like crabgrass
• Has deep roots and underground rhizomes
• Survives winter, returning stronger each year

✔ Seed Heads

• Has 2–5 dark purple-to-black seed spikes
• Seeds often appear sticky or moldy
• Seedheads rise tall above the grass canopy

✔ Seasonal Pattern

• Grows actively: Late Spring–Fall
• Dormant: Winter
• Returns each year

Because Dallisgrass is perennial, you typically see the same clumps in the same spots year after year.

🌱 Crabgrass Control (How to Get Rid of Crabgrass)

Controlling crabgrass is easier than controlling dallisgrass because crabgrass is an annual weed. Killing it once and preventing new seeds from sprouting is key.

🌿 1. Use a Pre-Emergent Herbicide (Most Effective)

Apply pre-emergent when soil temps reach 55°F for several days.

Examples of strong pre-emergents:

• Prodiamine
• Dithiopyr
• Pendimethalin

These prevent crabgrass seeds from germinating.

When to Apply:

• Early spring, before crabgrass sprouts
• In warm climates, two applications may be needed

🌿 2. Use Post-Emergent Herbicide for Active Crabgrass

Best for young crabgrass in early summer.

Products containing:

• Quinclorac
• Fenoxaprop-p-ethyl
• Dithiopyr (as early post-emergent)

These selectively kill crabgrass without harming most turf.

🌿 3. Manual Removal (For Small Patches)

Crabgrass has shallow roots—it pulls out easily mid-spring or early summer.

🌿 4. Improve Lawn Density

Crabgrass thrives in weak lawns. Prevent regrowth by:

• Overseeding
• Fertilizing
• Watering deeply
• Aerating
• Maintaining taller grass height (3–4 inches)

🌾 Dallisgrass Control (How to Get Rid of Dallisgrass)

Dallisgrass is much more difficult to eliminate. It grows back from roots and seeds and resists many common weed killers.

🌿 1. Selective Herbicides (Limited but Effective Options)

✔ MSMA (where legal)

Very effective but banned for residential lawns in many states.

✔ Celsius WG

Kills dallisgrass slowly but safely in warm-season lawns.

✔ Revolver

Effective on Bermudagrass lawns.

✔ Glyphosate (non-selective)

Kills everything it touches—best for spot treatment.

🌿 2. Repeat Treatments Are Necessary

Because Dallisgrass grows from rhizomes, you must:

• Treat early
• Treat again 2–4 weeks later
• Continue for multiple seasons

🌿 3. Digging Out the Clumps

Best method for small infestations.

Steps:

1. Use a shovel or weed knife
2. Remove entire root system
3. Replace soil
4. Reseed or patch with sod

If you miss any rhizome pieces, the plant comes back.

🌿 4. Mow Properly

Mowing high helps desirable grass outcompete Dallisgrass.

🌿 5. Improve Drainage

Dallisgrass loves wet areas. Fix:

• Overwatering
• Poor drainage spots
• Irrigation leaks

🟩 Dallisgrass vs Crabgrass: Key Differences (Detailed)

✔ 1. Lifecycle

• Crabgrass: Annual
• Dallisgrass: Perennial

✔ 2. Growth Pattern

• Crabgrass spreads outward low and wide
• Dallisgrass forms big upright clumps

✔ 3. Root System

• Crabgrass: Shallow
• Dallisgrass: Deep, rhizomes

✔ 4. Seed Heads

• Crabgrass: Thin finger-like
• Dallisgrass: Thick dark spikelets

✔ 5. Difficulty to Control

• Crabgrass is easier—one season of treatment
• Dallisgrass takes multiple seasons and multiple methods

✔ 6. Seasonal Behavior

Crabgrass dies each winter; Dallisgrass survives and regrows.

🌱 Prevention Tips for Both Weeds

✔ Maintain a thick lawn

Thick turf prevents weed seeds from touching soil.

✔ Fertilize properly

Weak grass invites weeds.

✔ Mow higher

Shading soil keeps weeds from germinating.

✔ Water deeply, infrequently

Shallow frequent watering encourages crabgrass.

✔ Fix bare patches

Weeds invade open spots quickly.

🌾 Which Is Worse: Crabgrass or Dallisgrass?

Crabgrass is annoying

…but manageable with pre-emergent and post-emergent herbicides.

Dallisgrass is much harder to kill

It grows back each year, survives winter, and resists many chemicals.

If untreated, Dallisgrass takes over large areas rapidly.

🌱 Crabgrass vs Dallisgrass: Visual Differences Summary

🔚 Final Thoughts

Both crabgrass and dallisgrass are invasive, fast-growing weeds that can ruin the appearance and health of your lawn. However, they require very different strategies:

✔ Crabgrass

• Prevent in early spring
• Kill young plants in summer
• Strengthen lawn to stop recurrence

✔ Dallisgrass

• Requires targeted herbicide
• Usually needs repeated treatments
• Digging out clumps is often necessary
• Prevention takes sustained effort

With proper identification, treatment timing, and lawn care practices, you can dramatically reduce or even eliminate both weeds over time.

David Holtzman

I’m David man behind Lawn Mowerly; I’ve been dealing with lawnmowers and Tractors with my father since I was a kid. I know every make and model and what each one is capable of and love helping people find the perfect equipment for their needs.