Dallisgrass and crabgrass are common species of grass that can show up in your yard uninvited, forming unsightly clumps and ruining the look of your nice, uniform lawn.
But how do you tell them apart? At a glance, they can appear quite similar.
This article will show you how to tell them apart and explain some pointers on how to control them.
Contents
- Key Differences Between Dallisgrass and Crabgrass
- Dallisgrass vs Crabgrass
- How to Control Dallisgrass (Paspalum dilatatum)
- How to Control Crabgrass (Digitaria sanguinalis)
- Summary
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Key Differences Between Dallisgrass and Crabgrass
While some grass species are easy to tell apart, dallisgrass and crabgrass have enough similarities that unless you’ve got them side by side, it could be hard to tell what you’re looking at.
They both have broad leaves and grow in clumps, forming patches of coarse grass that stand out against your finer lawn species.
Luckily, there are some key differences between dallisgrass vs. crabgrass that will make identification easy once you know what to look for.
These are:
- The growth formation. Dallisgrass grows in messy clumps but can spread into a thick mat while crabgrass will always have distinct star-like clumps.
- The root structure. Dallisgrass has deep rhizomes while crabgrass has a shallow root system.
- The seed heads. Dallisgrass has thick seed heads with black specks and crabgrass has fine seed heads with no black specks.
- The height. Left alone, dallisgrass will grow much taller than crabgrass which will stay low to the ground.
- The lifecycle. Dallisgrass is perennial and crabgrass is annual.
- The seasonal preference. Dallisgrass prefers cooler weather while Crabgrass thrives in warm temperatures.
Let’s look at these differences in a bit more detail…
Dallisgrass vs Crabgrass
Dallisgrass and crabgrass both have the potential to be very invasive in your yard. But, how successful they are depends on the health of your lawn.
They are opportunistic and like bare patches of soil, so if you don’t have any bare patches, they are unlikely to become a serious problem. Regardless, many homeowners would still prefer not to have these unsightly clumps growing in their lawn.
When it comes to identification, the most distinctive difference between dallisgrass and crabgrass is in the seed head.
Quick tip: Admittedly, this isn’t the ideal form of identification as you don’t really want to let either of these seeds get as far as growing seed heads if you’re trying to control them! But, if seed heads are already present, it’s a failsafe way of telling them apart.
Dallisgrass seed heads are much thicker and grow out of the sides of the stem as well as the top, with little black protrusions.
Crabgrass seed heads on the other hand are much finer and usually just grow out of the top of the stem (see images below).
Another key difference is in their root structure. To tell them apart this way will require a little digging (excuse my pun).
Dallisgrass grows from a deep rhizomatous root system which is also how it spreads, while crabgrass roots are shallow and leaving some in the ground when you pull out a clump probably won’t result in a new plant.
So, how can you tell them apart if you haven’t dug them up or let them go to seed?
They have a slight difference in color and growth formation.
While they both grow in clumps, crabgrass forms clumps that are more distinctive with the stems branching out from the center in a star-like formation, or like the legs of a crab which is how it got its name.
Dallisgrass grows taller than crabgrass, while crabgrass typically grows along the ground below the height of a typical lawnmower (annoying, right?).
Finally, there is a slight difference in color. Dallisgrass has a slightly more blue tinge to its green while crabgrass is slightly more yellow.
Another easy way to tell apart dallisgrass versus crabgrass will depend on the time of year.
As crabgrass is an annual, it will die off in the winter and leave dead patches in your lawn, returning in the spring from the seed stock that it left behind at the end of the previous summer. Dallisgrass on the other hand is perennial and can grow all year round.
| Dallisgrass | Crabgrass |
| Grows from rhizomes | Grows from seeds |
| Can survive all year round | Dies off in winter and grows back in spring |
| Grey-green color | Yellow-green color |
| Grows in dense clumps of no formation | Grows in star-shaped clumps |
| Grows a little taller than standard lawn height | Grows low to the ground |
| Thick seed heads with black spots that grow out of the sides and top of the stem | Fine, narrow seed heads that usually grow just out of the top of the stem |
| Prefers wet weather | Drought tolerant |
Not sure whether you have crabgrass or Bermuda grass? It’s not that hard if you know what to look for.
Or is it quackgrass you could be dealing with? We have an article explaining the differences between quackgrass and crabgrass so you’ll be sure you know what you’re dealing with.
How to Control Dallisgrass (Paspalum dilatatum)
Like any weed, the best method of control is to prevent it from establishing itself in your lawn in the first place. Once you have a thriving mat of dallisgrass, it will be very hard to get rid of!
Preventing the success of opportunist dallisgrass starts with keeping your lawn healthy and thick so you leave no room for invasive species to put down roots. Avoiding simple lawn care mistakes, mowing, watering, re-seeding bare spots and fertilizing appropriately, will give your lawn its best shot at fending off invaders.
Quick tip: Once you notice the arrival of dallisgrass, your best course of action is to completely dig it up, being sure to remove all of the roots to prevent it from returning. This is the only sure-fire way to remove it.
Alternatively, you can use glyphosate to spot treat your lawn, but as glyphosate will also kill your lawn species, you need to be really careful to avoid spraying anything else except the dallisgrass. Due to the strength of the rhizomes underground, one application is unlikely to be enough and you may need to repeat the process.
As with any pesticide, glyphosate should only be used as a last resort and sparingly due the negative impacts it has on the surrounding environment and soil health.
Once the dallisgrass has died and left a bare spot, you need to spread more grass seed there and avoid leaving it bare or it’ll likely become the home of another invasive weed.
Dallisgrass can also be managed by mowing your lawn with a catcher to remove any seed heads before they get a chance to spread. Many people underestimate the power of lawn mowing in maintaining a healthy lawn and controlling weeds. If you’re interested in learning more about lawn mowing, check out our tips here.
You can also use the same pre-emergent pesticides that are used for crabgrass seeds to kill any dallisgrass seed that might be in your lawn, but keeping your lawn short to prevent the growth of seed heads is the first choice.
New to lawn care? Have a read of our guide to lawn care tools before you get started.
And don’t forget to take care of the lawn once the grass starts to grow. Take a look at the different types of lawn mowers to find the one that fits your needs the most.
How to Control Crabgrass (Digitaria sanguinalis)
Assuming you’ve already done your best to maintain a healthy lawn and reduce the risk of crabgrass making itself at home, what can you do to remove it once it has arrived?
The management of crabgrass is actually pretty similar to dallisgrass, but easier in some ways. Crabgrass is really easy to dig out because it has shallow roots, and you don’t have to worry too much if you leave some behind – they’re not rhizomes so they can’t grow new plants.
The hard part about crabgrass is all the seeds they leave behind. So, regardless of which approach you choose to take, it’s going to be a multi-season mission.
You can dig up the plants that you can see, but then there could be many seeds still in the soil that could stay dormant for a number of years and pop up when you least expect it.
The easiest way to take care of all the seeds is to use a pre-emergent herbicide to make them non-viable at the beginning of spring. Unfortunately, this will mean that all seeds, including seeds you want, will be rendered useless. So in order to complete the job, you’ll need to sprinkle the lawn with fresh grass seed afterward to keep your lawn as dense and healthy as possible.
There are also certain lawn management practices you can use that will be less favorable to crabgrass.
These include:
- Mowing your grass a little longer to shade out the soil (crabgrass likes it hot).
- Mowing frequently to promote lush growth of the species you want to keep while removing any crabgrass seed heads.
- Watering less frequently but deeply to support the lawn species you want (crabgrass will thrive with more frequent, shallow watering while your lawn will suffer).
- Fertilizing in autumn or winter when crabgrass is dying or dead will mean that you can support your favorable lawn species without fuelling crabgrass.
It is actually possible to fight crabgrass without the use of pesticides if you learn how to manage crabgrass naturally.
Summary
Hopefully, you feel confident in identifying crabgrass and dallisgrass now. They are similar, but once you’re aware of their differences, you’ll have no trouble telling them apart. If in doubt, have a little dig and check out the roots!
Remember that the most effective control is preventing them from establishing themselves in the first place. Keep a close eye on your lawn, spot weed small patches of both dallisgrass and crabgrass if it arrives, and keep your lawn healthy and dense to limit the possibility of more invasions.
Have you had either of these grasses on your lawn? How did you get rid of them? Did it work?