12 Common Lawn Weeds, How to Tell Them Apart, and What Each One Means

A weed is just a plant that is better suited to your lawn than your grass is. That sounds like a throwaway line, but it is the most useful thing to know, because it means the weeds you have are diagnostic.

Crabgrass says you mow too short. Clover says your soil is short of nitrogen. Moss says shade and compaction. Plantain says the ground is packed hard. Fix the condition and you stop refighting the same battle every June.

Here are the twelve you are most likely to be looking at.

Broadleaf weeds

1. Dandelion. Deep toothed leaves in a flat rosette, hollow stem with milky sap, unmistakable yellow flower. Taproot goes down 25cm or more, so pulling the top does nothing.Compacted or thin turf
2. White clover. Three rounded leaflets, often with a pale crescent, small white flowerheads. Fixes its own nitrogen, which is why it thrives where grass is starved.Low nitrogen
3. Broadleaf plantain. Broad oval leaves in a flat rosette with strong parallel veins, and a stubby seed spike. Almost a definitive marker of compacted soil.Compaction
4. Creeping charlie. Scalloped round leaves on square stems, purple flowers, and a mint smell when crushed. Spreads by runners, so hand pulling leaves fragments behind.Damp shade
5. Chickweed. Small pointed oval leaves in opposite pairs, tiny white star flowers, and a single line of hairs running up one side of the stem.Damp, fertile, cool
6. Oxalis or wood sorrel. Looks like clover but with heart shaped leaflets and yellow flowers, plus seed pods that fire seeds when touched.Thin turf
7. Purslane. Fat succulent reddish stems flat to the ground with paddle shaped leaves. Loves heat and bare soil.Hot, dry, bare patches

Grassy weeds

1. Crabgrass. Coarse light green blades spreading flat from a central point like a spider. Annual, germinates when soil hits about 55°F for several days.Mowing too short
2. Annual bluegrass. Fine light green, seeds even when mown very low, dies off in summer heat leaving bare patches.Overwatering, compaction
3. Nutsedge. Looks like grass but the stem is triangular in cross section. Roll it between your fingers and you feel the edges. Bright glossy green and grows faster than the lawn, so it stands proud days after mowing.Poor drainage
4. Quackgrass. Coarse blue green blades with clasping structures where the leaf meets the stem, spreading by aggressive white underground rhizomes.Disturbed soil

And the one that is not a weed at all

Moss. It is not competing with your grass. It is occupying ground where grass has already given up. Killing the moss without changing anything gives you bare soil, and the moss comes back.

Moss means some combination of shade, compaction, poor drainage and acidic soil. Address those, usually with aeration, thinning overhead branches and a soil test, or accept that a shady corner is going to be a moss corner and enjoy it. Moss lawns are genuinely pleasant.

The four fixes that do most of the work

Mow higher. Most people cut far too short. Raise the blade to 7 to 9cm, or 3 to 3.5 inches, for most cool season grasses. Taller grass shades the soil surface, and crabgrass and most annual weeds need light hitting bare soil to germinate. This one change does more than any herbicide.

Water deeply and rarely. Roughly 2.5cm or one inch a week, in one or two soakings, not a light sprinkle daily. Shallow frequent watering grows shallow roots and favours weeds.

Aerate compacted ground. If plantain, moss or annual bluegrass dominate, the soil is packed. Core aeration in autumn, or spring for warm season grass, opens it up.

Feed and overseed. Thin turf is an invitation. Overseed in early autumn so grass occupies the gaps before weeds do. And if you have a lot of clover, that is a nitrogen deficiency telling you the lawn is hungry.

Before you spray anything

Identify it properly first. Broadleaf herbicides do nothing to grassy weeds, and products for crabgrass will not touch nutsedge, which needs a specific sedge product. People burn a lot of money and a lot of lawn spraying the wrong thing at the wrong time.

Timing matters as much as product. Pre-emergent for crabgrass has to go down before soil temperatures reach about 55°F, which in much of the US means when the forsythia blooms. After it has germinated, pre-emergent is useless.

And check whether you want to kill it at all. Clover was standard in lawn seed mixes until broadleaf herbicides arrived in the 1950s, it stays green in drought, it feeds pollinators and it fertilises your grass for free. A lot of people are now deliberately seeding it back in.

If you are not sure what you are looking at, photograph a single plant against a plain background with the base visible, since how leaves attach at ground level is what separates most lookalikes. Identium will name it and tell you whether it is worth pulling.