Lawn Weed Identification Guide (What Is This Weed?)

Start by deciding whether it is a broadleaf weed or a grassy weed, because that determines everything about how you kill it. Broadleaf weeds have wide, flat leaves with branching veins and usually produce flowers (think dandelion, clover, plantain). Grassy weeds have narrow, bladed leaves that look like your lawn grass (think crabgrass, foxtail, quackgrass). Once you know the category, compare your weed to the photos in this guide and read the quick tell for each to confirm the exact species. Look at the growth habit (upright, sprawling mat, or clump), leaf shape and arrangement, color, any flowers or seedheads, and when it greens up or dies. Getting the exact species right matters, especially for grassy weeds, because the correct product depends entirely on which weed you have.

Broadleaf weeds are a completely different type of plant from your lawn grass. They have wide, flat leaves with veins that branch out in a net pattern, and most produce recognizable flowers. Because they are so different from grass, a single selective herbicide (a 3-way broadleaf killer) can wipe out over 250 of them at once while leaving your lawn unharmed. Grassy weeds, on the other hand, are grasses, closely related to your lawn, with narrow blades and parallel veins. That similarity makes them much harder to control: there is no single product that kills all grassy weeds, and some cannot be selectively killed at all. This is why identifying which category, and which exact species, you are dealing with is the essential first step before buying any product.

Nutsedge is technically neither a broadleaf weed nor a true grass, it is a sedge, a distinct plant family. It is easy to mistake for a grassy weed because it grows among the grass and has narrow, blade-like leaves, but it gives itself away with a few tells: its stem is distinctly triangular (roll it between your fingers and you will feel three sides), its leaves are thick, waxy, and glossy, arranged in sets of three, and it grows noticeably faster and taller than your lawn, especially in the days after mowing. Because it is a sedge, it is not controlled by broadleaf herbicides or by most grassy weed killers, it needs a sedge-specific product like halosulfuron. We include it in this guide because people naturally look for it among the grassy weeds.

Because using the wrong product wastes money, wastes a season, and can even damage your lawn. Broadleaf herbicides do nothing to grassy weeds, and grassy weed products each target specific species, so a random spray often does not work. Worse, some perennial grassy weeds have no selective option at all, meaning the only fix is a non-selective herbicide plus reseeding, and if you did not identify that correctly you might keep buying selective sprays that can never work. On the flip side, spraying a non-selective like glyphosate on a weed you could have killed selectively leaves a dead patch of lawn you now have to reseed. Correct identification points you straight to the one approach that actually works, which is exactly what this guide is built to do.

On Long Island and across the Northeast, the broadleaf weeds you will see most are dandelion, white clover, broadleaf plantain, common chickweed, henbit, and the tougher trio of oxalis, ground ivy (creeping charlie), and wild violet. Among grassy and grass-like weeds, the big ones are crabgrass, annual bluegrass (Poa annua), yellow nutsedge, foxtail, goosegrass, nimblewill, quackgrass, and coarse tall fescue clumps invading a finer lawn. Which ones show up depends on your lawn's conditions: thin, compacted, or stressed turf invites the most invaders, while a thick, healthy, properly mowed lawn resists nearly all of them. This guide covers 24 of the most common offenders so you can identify yours and go straight to the fix.