What Does Crabgrass Look Like?

  • 01 of 06

    What Does Crabgrass Look Like?

    Photo of showing what crabgrass looks like. The growth habit explains its name origin.
    The crab came to mind when this weed was named because of the plant's tenacity, bending stems, and the way it hugs the ground. The picture shows a mature plant (the U.S. 10-cent coin at right gives a sense of scale). David Beaulieu

    My goal in this series of pictures is to answer the question, What does crabgrass look like? The best way to answer such queries is to provide photos of different plant parts (leaves, seed head, etc.). Thus the need for more than just the image above, which illustrates the weed's overall appearance in late summer.

    Once you have a positive identification on it, you can learn how to get rid of crabgrass. Note that the methods available to you are not limited to using crabgrass killers.

    In...MORE addition to supplying a bird's-eye view of crabgrass (whose botanical name is Digitaria), the picture above will explain to curious minds why it is that we have named this weed after the lowly crab. What comes to mind when you think of the appearance of this crustacean? That it is tough, many-legged and built low to the ground, with its legs bent, correct? Well, replace "many-legged" with "multi-stemmed," as well as "legs bent" with "stems bent," and the description fits crabgrass. Moreover, the weed, like the crustacean, is not only tough, but also famously 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 (as in my photo above), or popping up through a crack in the sidewalk. 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, such as alongside a driveway or right smack in the middle of a sidewalk. 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.

    But I promised to reveal what crabgrass looks like through images of individual plant parts, and on Page 2 I'll begin by showing you a closeup image of a plant part that will help you distinguish one type of crabgrass from another....

    Continue to 2 of 6 below.
  • 02 of 06

    Types of Crabgrass: Smooth, Hairy

    Photo of a type of crabgrass: smooth. Distinguish it from
    One type of crabgrass: "smooth" (Digitaria ischaemum). This kind has hairs at the auricle, but generally none elsewhere. David Beaulieu

    It may surprise some to learn that there are different types of Digitaria: my pictures reveal what smooth crabgrass looks like, but there is also a kind called "hairy" crabgrass. You're more likely to find the former in your lawn, which is why I've made it the focus of this article.

    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...MORE 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, precisely, those few hairs are located.

    Thus my picture above. This is a shot of a plant part on smooth crabgrass called an "auricle." What the heck is that? perhaps you ask. I assure you it has nothing to do with "oracle" (although the pronunciation is similar), which may call to mind either a computer software company or one of those shrines in the Greco-Roman world where prophecies were delivered, such as the oracle at Delphi in ancient Greece.

    No, botanically speaking, an auricle is a small, ear-like projection on the interior side at the base of a leaf. The reason I bring it up here is simply that it helps us identify smooth crabgrass and distinguish it from its much hairier relative. See the little hairs in the picture? You'll find them only at the auricle in the case of smooth crabgrass.

    On Page 3 we'll look at another of the plant parts of smooth crabgrass....

    Continue to 3 of 6 below.
  • 03 of 06

    Identification of Crabgrass (Smooth): the Leaves and Stems

    Photo for identification of crabgrass. Smooth crabgrass has a 5-inch leaf and bent stem.
    Smooth crabgrass bears a leaf blade that is about 5 inches long (maximum). The bent stem (upper right) should also aid you in identification. David Beaulieu

    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. My photo shows not only this tapering, but also (in the upper right-hand corner) how the stems bend at the nodes. These stems sometimes turn red in color. All these clues can aid you in identification.

    Peter del Tredici, in , says that smooth crabgrass also goes by the following common names:

    • Small crabgrass
    • Fingergrass
    • T...MOREwitchgrass

    The "small crabgrass" moniker derives from the fact that Digitaria ischaemum is 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."

    On Page 4, I help you identify smooth crabgrass further by revealing what it looks like when it's a younger plant, which will also give me a chance to discuss the life cycle of crabgrass -- knowledge that will come in handy when you're trying to eradicate it....

    Continue to 4 of 6 below.
  • 04 of 06

    For Crabgrass Prevention, Learn the Life Cycle of Crabgrass

    Picture: crabgrass before it sets seed. Crabgrass prevention means stopping germination.
    Picture: this plant first emerged in spring, from seed that germinated from one of last year's plants. It has not yet flowered and produced seed, itself, but will do so shortly. Crabgrass prevention is easiest if you focus on stopping germination. David Beaulieu

    Why bother learning about the life cycle of crabgrass? Well, you've heard the expression "an ounce of prevention is worth a pound of cure," right? Well, keep that saying front and center in your mind when trying to control this weed, because crabgrass prevention (i.e., keeping it from emerging in the first place) is a lot easier than trying to eradicate it after the fact.

    But to follow through on that strategy, you have to acquaint yourself with the facts behind this lawn weed's...MORE "rise and fall," if you will -- in other words, the life cycle of crabgrass.

    As I said on Page 1, 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.

    Why should it make any difference to you in your crabgrass-prevention efforts that this weed is an annual? An annual plant lives for only one year, during which year its one and only mission is to produce seed -- that's 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.

    The question, therefore, becomes, "How do I 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. Why? Because 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 -- seeds that will sprout next spring in your lawn, unless you prevent them from doing so via a pre-emergent herbicide. That's precisely the weed-control method I elaborate upon in my article on how to get rid of crabgrass.

    Speaking of crabgrass seeds, I have yet to show you what the plant's flower-head/seed-head looks like. I'll rectify that on Page 5....

    Continue to 5 of 6 below.
  • 05 of 06

    How Does Crabgrass Spread?

    Crab grass photo.
    Crabgrass flower-head photo. David Beaulieu

    The answer to the question, How does crabgrass spread? should be apparent from the prior page (which dealt with this weed's life cycle): it spreads by seed. The picture above shows the flower head of crabgrass (do you see now why an alternate common name is "fingergrass?"), and its seed head looks very similar.

    There's both good and bad news to be found in the conclusion that crabgrass spreads by seed.

    First the good news: crabgrass is limited in the way it can spread, compared to...MORE 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.

    Such is not the case with crabgrass. Stop the seeds from germinating, and you've stopped the plant -- period. But here's the bad news: to prevent germination, timing is of the essence (if you haven't already, read my article on getting rid of crabgrass, where I tell you about the timing and supply an easy way to remember it). Time your prevention efforts wrong, and you're stuck with crabgrass in your lawn for another summer.

    On Page 6 I'll conclude by mentioning a few other grassy weeds....

    Continue to 6 of 6 below.
  • 06 of 06

    Purple Love Grass, Other Grassy Weeds

    Picture: purple love grass. This grassy weed is often seen along roadsides.
    Purple love grass (Eragrostis spectabilis) is commonly seen along roadsides. En masse it will turn the heads of wild-plant enthusiasts, despite the classification "grassy weed.". David Beaulieu

    Eragrostis spectabilis is the rather ugly scientific plant name of a pretty wild plant called "purple love grass" (sometimes spelled "lovegrass"). There's a less pretty relative commonly called "tufted lovegrass" (Eragrostis pectinacea). E. spectabilis may be a grassy weed, but with this kind of beauty (picture above), I don't have much incentive to try to get rid of it.

    Whoever bestowed upon it its botanical name apparently would agree with me, since the specific...MORE epithet, spectabilis indicates "showy" in Latin. We find the same specific epithet in the botanical name for the most common type of bleeding hearts, a whimsical perennial flower.

    But there are other grassy weeds that, like crabgrass, offer little in the way of aesthetic value, and most homeowners will wish to get rid of them. In the examples that follow, I offer a mixed-bag (i.e., some of these plants have redeeming features, others are just plain ugly):

    Examples of Grassy Weeds in the Northeastern U.S.

    • Nimblewill (Muhlenbergia schreberi)
    • Fall panicum, AKA panic grass, witchgrass (Panicum dichotomiflorum)
    • Switchgrass (Panicum virgatum)
    • Reed canarygrass (Phalaris arundinacea)
    • Yellow foxtail (Setaria glauca)
    • Barnyard grass (Echinochloa crus-galli)
    • Deer-tongue grass (Dichanthelium clandestinum)
    • Quack grass (Elymus repens)

    Swaths of yellow foxtail and purple love grass sometimes combine on roadsides, painting a very pretty picture in autumn (if you like red-yellow color combinations). Deer-tongue grass is bamboo-like in appearance.

    Meanwhile, canarygrass is related to the invasive, variegated ornamental, ribbon grass.

    Of course, "weed" is a subjective term. There are many common weeds that are beneficial. For example, learning about edible weeds and wild plants ​​may bring out the inner forager within you. But if you're a no-nonsense type who is seeking further help in achieving an immaculate lawn, you'll probably be more interested in my tips for growing greener lawns.