Posted on

is crabgrass seed head a weed

What Does Crabgrass Look Like?

Much like the crab of the ocean, crabgrass (Digitaria) is tough, has many legs (or stems), and is built low to the ground. Its procumbent growth habit is one reason why this annual weed is so successful, whether it be in the lawn, growing along a driveway, or popping up through a crack in the sidewalk.

What Is Crabgrass?

Crabgrass is the common name for a genus of plants (Digitaria) that includes both annual and perennial grasses. The species generally have wide, flat blades and produce long flower clusters and thousands of seeds per growing season.

Keeping a low profile in the lawn, crabgrass eludes the mower blade when we mow the lawn. And unlike taller weeds, there's not much that can "break" on it, so it holds up well to foot traffic, even in high-traffic areas. The one plant part on the weed that sticks up—the stalk that bears its flowers and, later, its seeds—is very tough and does not mind being tread upon.

Crabgrass Varieties

It may surprise some to learn that there are different types of Digitaria: smooth crabgrass and hairy crabgrass. You're more likely to find the former in your lawn.

As you might imagine, the hairy type (Digitaria sanguinalis) is so-called because, if you inspect its leaves and stems, you will find many small hairs all over the plant. Likewise, the common name of the smooth type derives from the fact that its leaves and stems are relatively hairless.

But that does not mean that smooth crabgrass (Digitaria ischaemum) has no hairs at all. It does have a few, but it's a matter of where those few hairs are located. The hairs on smooth crabgrass are located only at the plant's auricles—small, ear-like projections on the interior side at the base of the leaves.

At maturity, the leaves of smooth crabgrass can measure as much as 5 inches long, although many factors influence the length of a particular blade. The leaf blades taper to a point. The plant's stems bend at the nodes, and the stems sometimes turn red in color.

Smooth crabgrass is also called "small crabgrass" because it tends to be smaller (6 inches maximum, but frequently shorter) than its hairier cousin, Digitaria sanguinalis. The latter, in fact, bears the alternate common name of "large crabgrass."

The Spruce / Adrienne Legault

The Spruce / Adrienne Legault

The Spruce / Adrienne Legault

Life Cycle

In addition to recognizing mature crabgrass, it helps to know what it looks like when it's a younger plant as well as its life cycle. This knowledge comes in handy when you're trying to eradicate the weed because the best way to control crabgrass is to keep it from emerging in the first place rather than trying to kill mature plants.

Crabgrass is an annual weed. It emerges in early summer, and it thrives during the hot weather because it is drought-tolerant. In fact, it’s often the last green thing in the lawn in August, before its stems are finally killed by the frosts of fall.

An annual plant lives for only one year, and at the end of the growing season, it's one and only mission is to produce seed. That is its life cycle, in a nutshell. The only way it can continue to be a problem for you in the following year is if it sets seed. So if you're fighting crabgrass in your lawn currently, it's because last year's plants (now dead) were successful in producing seed.

So, how do you break this cycle? You could try to stop the crabgrass in your current summer lawn from setting seed by spraying it with post-emergent herbicides. But you get more bang for your buck by preventing it from bursting upon the scene in the first place by using pre-emergent herbicides in spring.

Even if you're successful in killing it with a post-emergent herbicide, this doesn't prevent seeds from your neighbors' properties from landing in your yard. These seeds will sprout next spring in your lawn unless you prevent them from doing so with a pre-emergent herbicide.

How Crabgrass Spreads

The fact that crabgrass spreads by seed is both good and bad. First the good news: crabgrass is limited in the way it can spread, compared to a perennial weed such as, say, Oriental bittersweet. The latter can spread by seed, but it also spreads via rhizomes. So stopping the seeds of Oriental bittersweet from germinating in your yard won’t be enough to eliminate it: the plant lives to fight another day (year), even if it’s not successful in spreading itself via seeds.

With crabgrass, if you stop the seeds from germinating, you’ve stopped the plant, period. The bad news is that you have to get rid of crabgrass at the right time to prevent germination. Time your prevention efforts wrong, and you’re stuck with crabgrass in your lawn for another summer.

CRABGRASS PICTURES:
All Growth Stages

A Photo Gallery To Help Identify Crab Grass

Crabgrass pictures can be found in many resources, but are not always helpful. What do you do when the weeds you want to identify are much younger or older than the photo of crabgrass you have available?

It is important to know for sure, if crab grass is the weed you need to get rid of, especially if you find it in your lawn. Did you know that different growing conditions can cause amazing variations in plants, even those just a few feet apart?

The following pictures offer a good cross section of samples to aid in crabgrass identification.

You will also find links at the end of this article that give a detailed description of how this troublesome weed grows. An explanation of how to kill crab grass should also be useful.

Now let’s consider these crabgrass pictures.

FTC Disclosure: 
If you make a purchase via a link on this site, I may receive a small commission on the transaction – at no added cost to you.

CRABGRASS PICTURES 1:
Pictures of Crab Grass In Different Stages Of Growth

Crab grass seedlings, compared to a quarter for size. At this stage, the seedlings may still be susceptible to some pre-emergent weed killers.
Click here for more info on When to Apply Preemergents.
Or see a Users Guide: PreEmergents for Lawns
A young crab grass seedling already has a new side branch ready to shoot out.
The coin shows it is still a small plant, but this weed is already branching out in the typical crabgrass pattern. When crabgrass has room, it likes to spread.
The wide leaves, or blades, and dense growth are typical of crabgrass that has plenty of sun, moisture, and no competition.
This larger crab grass weed demonstrates the star shaped pattern often associated with crabgrass. You can be fooled when growing conditions are different than what this sample has encountered. Click here for more info and descriptions.
This is one crabgrass plant, though several weeds will often sprout together. Alone or in groups, they form a dense mat that smothers any competing weeds or grass.

CRABGRASS PICTURES  2:
Photos Of Crabgrass As It May Appear In Your Lawn

These pictures of crab grass show what the young seedlings look like when they first appear in your lawn. The manner in which the crabgrass then grows and develops will vary greatly. This photo collection should help you make the determination. Use the accompanying article at the end of this page for more description if you need it.

The wide blades and darker color make this weed stand out. Lawn grass that has a wide blade will be cut off square from mowing. The wide crabgrass blades will come to a point when they have not been cut.
A light, emerald green color is common for new crabgrass seedlings. This color, and the wide blades, help identify the weed in some lawns. This group of crabgrass seedlings is competing with each other and the lawn. They grow tall first, trying to dominate, before they sprawl out in their typical pattern.
This crabgrass looks barely different from the lawn grass. From certain angles, it may blend right in with some grasses. Look for wider blades that come to a point. When you see a patch that looks suspicious, use the technique in the next photo.
Run your hand across the grass in order to spread the dense growth. If you find this star shaped center hub, you know it’s a weed. Lawn grass will not flatten out like this.
Crab grass compared to bermuda grass. Crabgrass (on right) sends out runners (stolons), but not as far as bermuda grass. Crabgrass usually has a thicker stem, and wider leaves, but there are many varieties which could be larger than this sample of bermuda grass.
Since a bermuda lawn is often mowed shorter than other grasses, crabgrass can get started quickly when bare ground appears, especially in areas that get a lot of activity or suffer the effects of inadequate irrigation.
As crab grass matures, it forms a clump or mat. This usually grows faster than the lawn, so it is very noticeable a few days after mowing. It will kill off any grass trying to grow through it, if left untreated. Click here for more info.

CRABGRASS PICTURES  3:
As Crabgrass Matures And Goes To Seed

Hopefully, these last photos won’t be the key to your crabgrass identification quest. If they are, then you have missed the best time to eliminate this weed. Still, try to prevent any more seeds from forming than necessary, because this is the source of next year’s crabgrass problem.

This plant is mature, and will soon put out seed stalks from each branch and the center of the plant. It keeps growing, even after producing seeds, until it finally dies in cold weather. Kill it now and prevent next year’s problems.
This mature weed is producing seeds like crazy. The clump is two feet across. Hairy crabgrass can get even wider and taller when not mowed in a lawn.
The crabgrass seed head is quite similar to that of bermuda grass, but the stalk is usually taller and thicker. This sample shows a stalk that is 10 inches tall. It can be much taller, but can also be only 1″ – 2″ if the plant is frequently mowed, or is growing in hostile conditions (e.g. – little moisture or heavily shaded).

Thank you for visiting the Garden Counselor’s Gallery of Crabgrass Pictures.

NEED MORE INFO? Check out the links below to access additional articles with detailed information. 
More pictures of crabgrass are provided, plus descriptions and control methods that will help you find and eliminate this pest. 

What Does Crabgrass Look Like:
A detailed explanation to help you understand some of the differences seen in this photo gallery.

Pre-Emergent User’s Guide:
to learn about preventing lawn weeds and crabgrass.

Lawn Weeds: 
general info page, if crabgrass isn’t your only concern. 

Crabgrass – July Weed of the Month

July’s featured weed is Digitaria aka crabgrass.

The most common crabgrass in the Southeast is large crabgrass, Digitaria sanguinalis.

Everybody knows the name, but doesn’t know what to do about it. Walk with us through the weed patch to discuss crabgrass and what to do about this common weed.

Viewing Tip: Increase the volume and the playback speed according to your preferences. Volume control is the speaker icon on the lower left; playback speed is the gear button on the lower right.

Watch our Weed of the Month from our Lawn Tips Live recorded live at our Cartersville, GA store to learn more about these two look-alikes.

Viewing Tip: Increase the volume and the playback speed according to your preferences. Volume control is the speaker icon on the lower left; playback speed is the gear button on the lower right.

Large Crabgrass ID Features:

  • Family: Crabgrass is an annual plant in the Poaceae family, commonly called the grass family.
  • Habit: It starts from a central crown, then sprawls in a crab-like fashion. Hence, crabgrass.
  • Flowers: Grassy, green-colored flower and seed heads with 7 to 10 racemes.
  • Leaves: Large blades that give it a coarse texture and are larger than any lawn grass.
  • Stems: Large crabgrass has burgundy (reddish brown) stems that root at the nodes. This color and the nodal rooting are important identification features. The stems of “large crabgrass” are slightly hairy, though the stems of “hairy crabgrass” are remarkably more hairy and once you see hairy crabgrass, you’ll easily tell the difference between the two.

Sprawling large crabgrass that found purchase in a bare spot without mulch.

Sprawling and more crab-like habit of large crabgrass that found a place to germinate in fire pit rocks, with a visible center crown.

The center crown showing hairy stems and the reddish brown stems.

Note the reddish brown stems, the hair on the leaves, and the roots forming at the leaf nodes.

Flower head of large crabgrass showing 8 racemes.

There are many different types of crabgrasses in the Southeast. If you’re a beginner at learning weeds, just getting it to the level of crabgrass is a great start. Besides large crabgrass, you’re most likely to find smooth crabgrass. It is less hairy, has shorter leaves, and grows in a tighter clump.

Learn more about large crabgrass from these websites:

  • NC State Extension lists several crabgrasses & related species
  • Clemson Home & Garden Information Center has a general article on crabgrass species
  • UGA has crabgrasses listed in its database

There are two look-alikes, dallisgrass and goosegrass, that we’ll explore in a later episode, but I want you to be aware of them if you’re in doubt if you have large crabgrass or not.

Eat it or Treat it

Crabgrasses are in the Poaceae family and are technically edible. It takes a lot of work to harvest their seeds by hand, though this is a useful foraging tip if you’re entering one of those survivalist TV shows.

Prevention:

  • #1 Best tip for Crabgrass Control: In February spread pre-emergent herbicide to prevent germination of summer weeds, such as crabgrass. Crabgrass germinates early in winter so if you have a crabgrass infestation, we recommend you don’t miss applying pre-emergent in early February. If you subscribe to our email we’ll send you an email reminder or sign up for Lawn Coach and we’ll send the pre-emergent to you at the right time.
  • Prevent crabgrass in beds with thick layers of mulch and by cultivating a thick, healthy lawn.

Manual:

  • Hand pull – It can become a big plant, but it’s easy to pull up by yanking it by the crown. I use a CobraHead long handle weeder that saves my back from stooping. With this tool I keep standing to snag the crown, pull it out, then with a flick of the tool toss it aside. Very satisfying.
  • Mow to keep larger plants from going to seed.
  • Time/Patience: Crabgrasses are annuals that will be killed by frost in autumn. Sometimes time/patience feels like hard manual labor, doesn’t it?

Chemical:

  • Use a post-emergent herbicide for grassy weeds, such as Quincept. However, don’t use Quincept on Centipede laws as Centipede is very sensitive to chemicals and it could possibly be destroyed. Quincept is safe for all other lawns. Always apply according to directions on the label and use a surfactant to help it stick.

    Since recording the video, we have learned that Tenacity, previously only available to licensed commercial applicators, is now available to homeowners for crabgrass control on Centipede lawns. Please test it on a section of your Centipede lawn before applying it to the entire lawn and carefully follow the directions on the label.

Order Quincept for shipment or schedule it for pick up at your local Super-Sod.