Dallisgrass vs Crabgrass (the differences are subtle!)

Dallisgrass and crabgrass are the stuff of nightmares for many gardeners when it comes to lawns and gardens, where they often cause significant damage. Identifying the differences between them is important to implement targeted control methods. 

Dallisgrass is a perennial that stands tall and proud with a unique seed head, while crabgrass is an annual that prefers to keep a low profile with a broader leaf blade. To effectively remove them, understanding their lifecycle and seasonal preference is actually quite important.

weed begins growing

Table of Contents

Dallisgrass vs Crabgrass

Distinguishing between dallisgrass and crabgrass can be difficult even for professionals. However, the seed head is the key distinguishing feature between the two weeds. Crabgrass seed heads are usually small and fine, while dallisgrass seed heads are larger and have small black spots. Let’s explore this in more depth below so you can understand some of the key differences between the two weeds.

Dallisgrass vs Crabgrass: Key Differences

Dallisgrass and crabgrass are both invasive lawn weeds, causing frustration for those attempting to maintain a pristine lawn. Understanding the key differences between these two weeds can help with accurate identification and the correct treatment.

Firstly, dallisgrass is a perennial weed, meaning it can grow back from its same root system each year, making it more tenacious than crabgrass, which is an annual weed that only grows from seeds year on year. This makes dallisgrass harder to control because it doesn’t die out once the season ends.

In terms of appearance, dallisgrass has a coarse texture and typically grows as a solid, circular clump. In contrast, crabgrass has a star-like pattern as it spreads outwards. The root structure of these two weeds is also different, with dallisgrass having deep rhizomes, while crabgrass features a shallow root system.

Another distinguishing factor between dallisgrass and crabgrass is their seed heads. Dallisgrass has thick seed heads with black specks, while crabgrass seed heads are fine and do not have any black specks. This difference in seed head appearance can be helpful when identifying the weeds in your lawn.

Identification

Distinguishing between dallisgrass and crabgrass is essential to effectively control and manage these invasive weeds. To help with identification, several features can be observed and compared.

Dallisgrass is a warm-season perennial grass that can grow up to 5 feet in height. It has a coarse texture and forms robust, clumping growth patterns. 

Dallisgrass has a distinctive greyish-green colour and can be recognised by the hairs that grow on the leaf collar and sometimes on the base of the leaf blade as well. This grass grows in an ever-enlarging circular clump, with the centre often dying out while the outer rings continue to expand source.

On the other hand, crabgrass is an annual weed with a different lifecycle compared to dallisgrass. It appears lighter green in colour and has smooth, folded leaves that form a distinct pattern. 

Crabgrass can be identified by its prostrate growth habit, as it often lies flat against the ground and spreads through stolons or runner-like growths source.

In terms of height, crabgrass typically grows shorter than dallisgrass, and its seed stalks are generally lower. Additionally, crabgrass has a more sparse and less invasive growth pattern than the aggressive, deep-rooted nature of dallisgrass source.

In summary, to identify the difference between dallisgrass, and crabgrass, one should consider the following key features:

  • Color: Dallisgrass is greyish-green, while crabgrass is lighter green.

  • Texture: Dallisgrass is more coarse-textured compared to crabgrass.

  • Height: Dallisgrass can grow taller than crabgrass.

  • Growth pattern: Dallisgrass forms dense, circular clumps, whereas crabgrass has a more prostrate growth habit.

  • Lifecycle: Dallisgrass is a perennial grass, while crabgrass is an annual weed.

  • Presence of hairs: Dallisgrass often has hairs on the leaf collar and the base of the leaf blade.

crabgrass stems

Lifecycle and Growth Patterns

Dallisgrass and crabgrass are two common weeds that compete with desired grass species in lawns and gardens. Despite their similarities, they exhibit significant differences in their lifecycle and growth patterns.

“Dallisgrass grows and reproduces both through seeds and its underground rhizomes. The extensive underground root system allows dallisgrass to form thick circular clumps on lawns. These clumps can reach heights of up to 5 feet, making them more difficult to manage.

On the other hand, crabgrass completes its entire life cycle in just one growing season. It relies heavily on seed production for its survival, with each plant capable of producing up to 150,000 fertile seeds. Unlike the tall and clumpy dallisgrass, crabgrass spreads outwards in a low-growing manner, resembling a star or a crab’s legs.

Both of these weeds exhibit different spreading mechanisms. Dallisgrass tends to spread through its rhizomes and clumps, while crabgrass spreads mainly through its massive seed production. 

Additionally, dallisgrass thrives in cooler temperatures, whereas crabgrass prefers warm environments, allowing them to dominate in different climatic conditions.

weed free lawn

Weed Control and Prevention

When it comes to controlling and preventing grassy weeds like dallisgrass and crabgrass, the use of pre-emergent and post-emergent herbicides can be effective. These chemical control methods target the weeds at different stages of growth, ensuring a properly maintained lawn.

Pre-emergent herbicides aid in the prevention of weed germination. For both dallisgrass and crabgrass, pre-emergent herbicides should be applied before their seeds germinate. Timing is crucial, as applying the herbicide too early or too late can lessen its effectiveness.

In contrast, post-emergent herbicides are used to control weeds after they have emerged from the soil. These herbicides can target specific weeds, like dallisgrass and crabgrass, without harming your lawn. 

However, using post-emergent herbicides can require multiple treatments, especially for dallisgrass, which can be harder to eliminate due to its root system that allows it to grow back each year. 

Some common post-emergent herbicides for dallisgrass and crabgrass control are glyphosate, sulfonylurea herbicides, quinclorac, and tenacity turf herbicide.

Apart from herbicides, keeping your own lawn healthy and well-maintained is vital for weed control and prevention. A well-maintained lawn can outcompete weeds, reducing the possibility of weed infestation. 

Some essential lawn care practices include watering adequately, keeping the grass height at the right level, and maintaining proper fertilisation. Additionally, regular monitoring and addressing any lawn problems quickly can help prevent the spread of weeds.

selective herbicide

Lawn Care and Maintenance

Taking care of your lawn involves several key aspects to ensure a healthy and visually appealing landscape. Lawn care and maintenance encompass activities such as mowing, watering, fertilisation, irrigation, aeration, and general upkeep. 

Understanding the differences and similarities between dallisgrass and crabgrass can help you implement better strategies to maintain a healthy lawn.

Mowing

Mowing is obviously right up there when it comes to maintaining a well-groomed lawn. For both dallisgrass and crabgrass, cutting the grass at a proper height is crucial. 

Dallisgrass has a tendency to grow in clumps and can form a thick mat, while crabgrass often displays a distinct star-like pattern. Mowing the lawn regularly, and at the correct height can help minimise the spread of these grassy weeds.

Watering

Watering plays a vital role in the overall health of your lawn. To encourage the growth of desirable grass species and discourage the growth of dallisgrass and crabgrass, water the lawn deeply but infrequently. 

Proper irrigation helps promote a strong root system in your desired grass while weakening the more shallow-rooted crabgrass.

Fertilisation

Fertilisation is another component of lawn care. Providing your lawn with the appropriate nutrients will help it thrive and compete against invasive grass species. 

Crabgrass, for example, tends to establish in lawns with insufficient nutrients. Adjusting your fertilisation schedule to match the needs of your lawn can go a long way in preventing these weeds from taking over.

Aerating

Aerating your lawn is a beneficial practice that improves the soil structure and allows water, air, and vital nutrients to reach the grass’s root zone. This process benefits your chosen grass species while making it more difficult for dallisgrass and crabgrass to thrive.

Regular lawn maintenance is crucial in the battle against invasive grassy weed species. By using strategies such as monitoring your lawn for signs of infestation, implementing a preventive maintenance routine, and treating weed outbreaks promptly, you can effectively control the growth of dallisgrass and crabgrass.

controlling dallisgrass

Control and Prevention Tips

Controlling and preventing the growth of both dallisgrass and crabgrass is essential for maintaining a healthy and visually appealing lawn. Here are some tips for effective weed management:

  1. Pre-emergent herbicides: To prevent the emergence of these invasive weeds, consider the application of pre-emergent herbicides. This treatment should be applied diligently, as it helps reduce the germination of weed seeds.

  2. Post-emergent controls: If these weeds have already started growing in your lawn, you can apply post-emergent controls. However, this method will require multiple treatments and can be more expensive.

  3. Maintain a healthy lawn: A well-maintained lawn makes it harder for invasive weeds to establish themselves. Regular garden maintenance, such as proper mowing, watering, and fertilising, strengthens your grass and prevents weeds from thriving.

  4. Hand-pulling or digging: Physically removing small infestations of dallisgrass and crabgrass can be an effective method for control. Ensure that you remove the root system of dallisgrass, as it can grow back if not dealt with properly.

  5. Alternative weed killers: For those who prefer an eco-friendly solution, using vinegar as a weed killer can be an option. Be careful while applying vinegar, as it can affect your desired plants as well.

cutting lawn to prevent weed growth

Conclusion

Even professionals can have a hard time telling dallisgrass and crabgrass apart, but the seed head is the distinguishing feature. Crabgrass seed heads are small and fine, while dallisgrass seed heads are larger and have small black spots. If you are still unsure, make sure you contact a professional who will be able to advise you on the best course of action to take.

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Oliver Wright
Oliver Wright

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