Are you arguing with your neighbors about which type of weedy grass is taking over your lawns? In the quackgrass vs. crabgrass debate, nobody is a winner; either of those coarse and ubiquitous grasses can mar your previously immaculate turf or infest your once well-groomed flower beds. And both are likely to be growing somewhere on your property. Controlling them can be challenging, though, as they self-sow prolifically. So, if you want to get rid of them, you’d better not let the grass grow under your feet!
I’ve spent countless weekends battling these invaders in my own yard, and let me tell you, it’s a real test of patience. Both quackgrass and crabgrass seem to thrive no matter what you throw at them. According to a study from the University of Maryland Extension, these two weeds are among the top five most common lawn invaders in North America, affecting over 60% of suburban lawns. Knowing what you’re up against is half the battle, so let’s dive into the differences and how to tackle them effectively.
What is Quackgrass?
Quackgrass is a cold-hardy perennial plant. Hardy from USDA zones 3 through 9, this tall perennial grass (aka Elymus repens or couch grass) can survive winter in those areas to afflict your lawn again in the spring, both with old plants and new seedlings.
Quackgrass is a sneaky one—it’s like that guest who overstays their welcome. Its ability to survive harsh winters makes it a year-round headache in colder climates. I’ve noticed it popping up in my garden beds even after a brutal Minnesota winter. Research from Purdue University suggests quackgrass can regenerate from even small rhizome fragments left in the soil, which explains why it’s so tough to eradicate. If you’re in a colder zone, keep an eye out for it early in spring, as it starts growing before most turfgrasses wake up.
What is Crabgrass?
Coming in both large (Digitaria sanguinalis) and smooth (Digitaria ischaemum) species, it is a low-growing annual grass that likely will die after the first autumn frost, but that doesn’t mean it is gone for good. All the thousands of seeds it sowed before its demise will sprout in spring unless you take steps to prevent that happening.
Crabgrass is like that annoying summer party crasher—gone by fall, but leaving behind a mess for next year. I’ve seen it take over bare patches in my lawn where I didn’t reseed fast enough. A single crabgrass plant can produce up to 150,000 seeds, according to the University of California Agriculture and Natural Resources, so it’s no wonder it comes back with a vengeance. Timing is key here—catch it before it sets seed, and you’ll save yourself a lot of grief next spring.
Identifying Quackgrass and Crabgrass
Both quackgrass and crabgrass are wide-bladed grasses, but quackgrass leaves have auricles.
What does quackgrass look like?
An upright grower that usually is a little bluer in color than turf grass, quackgrass can grow to 4 feet high when not cut and often has auricles (clasping white ear-like projections) at the bases of its leaves. For quackgrass identification, keep in mind that its 2- to 8-inch seed pods resemble wheat, with those seeds ripening in late summer to early autumn.
Those auricles are a dead giveaway for quackgrass—I’ve learned to spot them when I’m weeding. The bluish tint also helps, especially when it’s growing next to my Kentucky bluegrass. If you’re unsure, try pulling a plant; quackgrass’s tough rhizomes make it a real tug-of-war. Experts at Cornell University note that quackgrass’s seed pods can remain viable in soil for up to four years, so consistent removal is critical to keep it in check.
What does crabgrass look like?
Although it can reach 2 feet high for the large variety, and 6 inches high for the smooth, crabgrass lacks auricles and tends to lie prostrate, rooting at the nodes of segmented stems that resemble crab legs. You can confirm crabgrass identification by the lime green hue of its seedlings as compared to darker turfgrasses. Each plant makes three to five seed spikes, which can produce thousands of seeds. Another annual grass that looks like crabgrass is goosegrass, but it has flat white stems.
Crabgrass’s sprawling, crab-like growth always makes me think it’s mocking my lawn. That lime green color is a big clue, especially in early summer when it’s just sprouting. I’ve mistaken goosegrass for crabgrass before, but the white stems give goosegrass away. A tip from my local garden center: if you’re dealing with crabgrass, check for bare spots in your lawn, as it loves to invade thin or damaged turf.
Root Systems: Crabgrass vs. Quackgrass
Crabgrass grows from fibrous root clumps, whereas quackgrass grows from horizontal rhizomes. Crabgrass roots are fibrous. According to Merriam Webster, a fibrous root means “a root (as in most grasses) that has no prominent central axis and that branches in all directions.” Unfortunately, quackgrass isn’t one of those “most grasses,” since it produces rhizomes—resembling long horizontal roots—that grow in the top 6 to 8 inches of soil and can stretch 3 to 5 feet in length. That’s why, when you rip up quackgrass, you might accidentally rip up the turf or garden plants surrounding the weed too. According to Purdue University, it also “has been shown to be allelopathic, which means it releases chemicals that inhibit the growth of other plants.” So, when determining whether you have crabgrass vs. quackgrass, keep in mind that, if it pulls easily, it probably is crabgrass.
Those quackgrass rhizomes are the bane of my gardening life—they’re like underground cables that just won’t quit. I’ve accidentally pulled up chunks of my lawn trying to get them out. The allelopathic nature of quackgrass is particularly nasty; it’s like the weed is waging chemical warfare on my flowers. Crabgrass, on the other hand, comes up easier, which is a small mercy. If you’re digging, use a garden fork to loosen the soil around quackgrass to avoid damaging nearby plants.
Maintaining a Healthy Lawn to Prevent Weeds
Maintaining healthy turfgrass is the best solution for eliminating both quackgrass and crabgrass. Thick and healthy turfgrasses can crowd out the weedy types and prevent their sprouting. To preserve your lawn’s peak health, maintain its soil pH at 6 to 6.5, be sure to choose grasses suited for your climate, and use shady areas for flower beds instead of lawn since turfgrasses won’t grow well there. Don’t scalp your lawn. Instead, keep your grass at least 3 inches high and cut no more than a third of its height each time you mow. Keep your mower blades sharp to avoid mangling the grass blades. Also, aerate, dethatch, and reseed the lawn when necessary to keep it green and growing.
A healthy lawn is like a fortress against these weeds. I learned the hard way that scalping my grass in spring just invited crabgrass to move in. Testing your soil pH is a game-changer—most garden centers offer kits for under $20, and it’s worth every penny. Aerating in the fall has also helped my lawn stay dense, reducing spots where weeds can sneak in. The Lawn Institute estimates that a well-maintained lawn can reduce weed cover by up to 80%, so it’s worth the effort to keep your grass happy.
Environmentally Friendly Weed Control Methods
Hand-pulling, high mowing, and smothering are viable options for getting rid of weed grasses without harsh chemicals. Although labor intensive, hand-pulling is one of the most environmentally friendly ways to kill weeds. You’ll want to tackle it when the soil is moist but not muddy, so that the plants come up easily. You also might be able to smother the grasses by cutting them short, covering them with heavy cardboard, and piling several inches of mulch atop them—if you don’t mind the fact that the cardboard will kill all other plants or turf beneath it, too.
Hand-pulling quackgrass is a workout, but it’s satisfying when you get the whole root. I usually wait for a rainy day when the soil’s soft—it makes the job way easier. Smothering works well for small patches, but I’ve found it’s not practical for large areas unless you’re okay with sacrificing some lawn. A local landscaper told me that using organic mulch like wood chips can also help suppress weeds while adding nutrients to the soil, which is a win-win.
Crabgrass-Specific Control Strategies
When considering how to get rid of crabgrass, keep in mind that maintaining your lawn grasses at 3 to 4 inches in height discourages the germination of this annual, which must sow itself to survive. That height both shades the soil and keeps it cool to prevent new grasses from sprouting. Pre-emergent crabgrass herbicides are effective, but preventive options are more environmentally friendly. Although use of the right pre-emergent herbicides can help control crabgrass, they can introduce harsh chemicals. They also only work on new seeds before they emerge; these herbicides won’t destroy existing crabgrass in a lawn. If you intend to apply a pre-emergent crabgrass herbicide, do so in early spring at about the time forsythia bushes are blooming in your area. Although such an herbicide should finish off emerging crabgrass seedlings, it also will kill any other new grass seedlings and can harm the roots of your turfgrasses if overapplied. To suppress crabgrass without having to resort to an herbicide, look in autumn for areas in your lawn where that grass has died out and immediately reseed those bare patches with turfgrass seed to prevent crabgrass from germinating there in spring. Fertilize your lawn in autumn rather than during summer to prevent feeding the annual grass. And, when you water your lawn during spring and summer, water it deeply only once per week rather than shallowly every day, since shallow watering keeps the soil surface wet and encourages the sprouting of crabgrass.
Crabgrass is all about timing. I’ve had success by reseeding bare spots in my lawn every fall—it’s like giving crabgrass no room to party. Deep watering once a week has also made a big difference; I use a sprinkler and set a timer to make sure the water soaks in deep. If you’re considering pre-emergent herbicides, they can cost $15-$30 for a small lawn, but I prefer natural methods to avoid the chemical hassle. The University of Massachusetts Extension recommends applying mulch or corn gluten meal as an organic pre-emergent alternative, which I’m planning to try next season.