Nutsedge: How to Kill It and Keep It Out

Nutsedge is a perennial sedge, and the answer to why it keeps coming back sits underground. The tubers, not the leaves you pull, decide next year. Plenty of people call it nutgrass. Those tubers grow on rhizomes 8 to 14 inches (20 to 36 cm) down, with most of them in the top 6 inches (15 cm), which is why a pass with a hoe changes nothing you can see by August.

NC State Extension records as many as 6,000 tubers from a single yellow nutsedge plant under optimum conditions. One plant can widen a patch to 10 feet (3 m) across. Yellow nutsedge and purple nutsedge both form tubers, and the two take different herbicides, so you name the species before you buy anything. The leaf tip and the seedhead color settle that in a few seconds.

Leaf count decides the timing, not the calendar. A spray works while the plant is young, at the 3 to 8 leaf stage, and it stops working once nutsedge tubers begin to mature in mid to late summer. Count leaves on a few plants in the patch before you treat. A tall, coarse stand has already stocked the soil for next year, and none of the home products control mature plants.

A patch is also a diagnosis. UC IPM says its presence often indicates poor drainage, too-frequent irrigation, or leaky sprinklers. The weed runs worst in heavy soils during a wet year and the year after that. Find the wet spot or the leaking head first. Otherwise you spray the same corner every July, the tubers in the soil keep sprouting, and the job stretches across several seasons.

How to get rid of nutsedge? Work it in order, because the order matters more than the effort. Confirm the plant, name the species, count the leaves, then work the same patch again in 2 to 3 weeks. UC IPM puts a tuber's spending at 60% of its reserves on the first plant and another 20% on the second. Pull that first shoot young and the tuber has little left to spend.

Leaf count is the field rule, and it sets a different threshold for each method. Pull shoots before the 5-to-6-leaf stage, because past that point the plant starts building tubers. If you spray instead, the herbicide window runs from 3 to 8 leaves, before tubers mature. Check a few shoots across the patch before you decide.

Early June, a tall fescue lawn on heavy clay, and I am counting leaves on a shoot that was not there in mid May. Six leaves. Clemson puts new tuber formation at 4 to 6 weeks after a shoot emerges, usually May or June once plants pass 5 to 6 leaves. I pulled it and flagged the spot to check again in 2 weeks.

Any nutsedge plan needs several years of sustained effort, so judge progress by how much the patch shrinks. A labeled sedge herbicide can kill nutsedge tops within days. The nutsedge tubers sitting in the soil set the real schedule, and steady nutsedge control means working the same ground every summer.

More than 40 sedge species grow in North Carolina landscapes alone. Nobody needs to name them all. You only have to separate nutsedge from whatever sits beside it, and one grip settles most of that. Roll a stem base between your thumb and index finger and feel for three flat sides instead of a round hollow tube. A triangular stem tells you it is a sedge, which is the first move when you identify nutsedge, and it takes no tools and no digging.

The nutsedge vs crabgrass question comes up because both green up fast in July heat while the lawn stalls. Look straight down at the base of the plant. Sedge leaves come off in sets of three. Grasses carry theirs in sets of two, on stems that are round and hollow. Crabgrass sprawls sideways across the ground, while nutsedge shoots straight up and stands above the turf a day or two after mowing. Strip the outer leaf sheaths off a stem base and you will often find a reddish tint underneath.

A tuber ends the argument. Trace a shoot down with a trowel, and a nut-like tuber at the tip of a rhizome confirms what your fingers already told you. An empty dig proves less than people think. Clemson puts new tuber formation at 4 to 6 weeks after a shoot emerges, so a young plant may not have grown one yet.

Green kyllinga and tall flatsedge pass the stem test and then fail the tuber test, because neither one forms tubers at all. That difference decides your whole plan. Tubers are the reason nutsedge comes back year after year, and a lookalike without them gives ground much faster.

So which one is in your lawn? Look at the seedhead first, because NC State Extension calls flower color and form the most reliable field difference between the two. Yellow nutsedge flies a yellow-green to tan seedhead and purple nutsedge carries a deep purple to black one. Leaf tips confirm the call. Yellow tapers to a long thin point and purple ends abruptly blunt. Dig a plant and you have the last piece, since yellow makes single round tubers at the tips of its rhizomes while purple runs its tubers in chains along them.

Size and sprouting temperature back up the reading. Yellow nutsedge reaches 12 to 16 inches (30 to 41 cm) at maturity and starts growing once soil holds above 43°F (6°C), so it turns up early and stands taller than the turf around it. Purple usually stays under 6 inches (15 cm) and waits for soil above 59°F (15°C). Yellow is the more widespread of the two because it handles cold better, and both species often grow together in the same yard.

The two species split on herbicide susceptibility, and that split is what makes nutsedge identification worth 5 minutes on your knees. Clemson rates bentazon good on yellow and poor on purple. Imazaquin runs the other way, fair on yellow and good on purple. Halosulfuron rates good to excellent on both, so buy that one if you cannot tell the two apart or if you have both. Read and follow the label before you mix anything.

One gap has no product answer at all. UC IPM says no preemergent herbicide controls purple nutsedge. Nothing you put down in spring stops it, so with purple you work with post-emergent sprays and a shovel.

How deep do nutsedge roots go? The rhizomes run 8 to 14 inches (20 to 36 cm) down, and most nutsedge tubers sit in the top 6 inches (15 cm) of soil. Those are the ones a spade can reach. The strands below that depth snap when you pull, and each broken piece still carries a live bud.

NC State reports that one yellow nutsedge plant can make as many as 6,000 tubers under the best conditions. Clemson dates the start of that run to 4 to 6 weeks after a shoot breaks the surface, usually May or June, once the plant passes 5 to 6 leaves. Every shoot you take before that window comes out of the tuber's account with nothing going back in. One plant's patch can reach 10 feet (3 m) across, and the rhizomes carry it there without a single seed.

Nutlets do not all wake up in the same spring. That is why a bed you cleaned in June can look infested the next year with no new plant arriving from anywhere. UC IPM puts tuber survival at 1 to 3 years, while NC State has recorded some sitting dormant up to 10 years. Tuber dormancy is not settled science, and the resprout counts split the same way, with UC IPM saying a mature tuber comes back more than 3 times and Clemson saying 10 to 12.

The patch at my back fence dropped from a dinner-plate clump to a few stragglers in one summer, and it started with a leaky sprinkler head I swapped out in May. A tuber spends 60% of its reserves on its first plant and 20% on the second, so I cut every shoot I could see every 2 to 3 weeks. By August the new blades came up thin and pale. The next spring, four plants.

Walk out to a midsummer patch and count the leaves on one shoot. That number sets your plan. Under 5 or 6 leaves, pulling still pays off, because the plant has not banked new tubers yet. Penn State puts the best time to treat nutsedge at the 3 to 8 leaf stage, before tubers mature in mid to late summer. Past that, on a stand of mature plants, no product controls them, so your goal for the rest of the year is limiting new tubers.

Species drives the choice more than the brand on the jug. Halosulfuron rates good to excellent on both yellow and purple nutsedge. Sulfentrazone works fast but rates fair on yellow and poor to fair on purple. Speed is not control. A sedge killer that browns a patch in 2 days is not the same as a nutsedge herbicide that finishes the job, so read the table below by species first and by speed second.

The weather rules matter as much as the product you buy. Do not spray postemergence products in hot, dry weather above 90°F (32°C). Water the lawn the day before so the plants are growing when you spray. Stop mowing 2 to 3 days before and after the application, since the herbicide needs leaf area to get in. Skip one of those and you get a patch that yellows for a week and comes right back.

In NC State trials, two halosulfuron applications at the lower label rate beat one at the higher rate. The cap is two applications per year. Add a nonionic surfactant at 2 teaspoons per gallon (10 ml per 3.8 L) and plan a repeat in 6 to 10 weeks. Watch the bed edge too. Imazaquin damages viburnum, pieris, azalea, birch, abelia, ligustrum and many hollies. Keep bentazon off sycamore, taxus and rhododendron, and read the label before the sprayer comes out.

One strip of my back lawn stayed spongy underfoot all summer, and the nutsedge there stood taller than the grass around it. From the kitchen window it read as a darker green stripe running toward the fence. I found the sprinkler head at that corner leaking at the base. It had been dripping for weeks and I never caught it, because the zone ran before dawn and the wet patch dried off by breakfast.

Nutsedge usually marks the wettest ground you own. UC IPM says it thrives in waterlogged soil, and that a patch of it often means drainage is poor, irrigation runs too often, or a sprinkler leaks. The patch is a reading of the site. It also turns worst in heavy soils through above-average-rainfall years and the year after, so a soaking spring can show up in your grass a season later.

Work down the list from cheapest to hardest. Overwatering is the easy one, because you own the timer and a shorter cycle costs you nothing. Switch to deep, spaced-out lawn watering so the surface dries out between runs. What is left after that is a nutsedge drainage problem, and that takes grade work or a drain line. Turf density does the rest once the water is under control. Steady mowing and feeding thickens the grass and slows the spread, though thick turf will not clear a stand that is already there.

In beds, skip the black or clear plastic sheeting. The sharp leaf tips puncture the polyethylene and the shoots come up through the holes. Nonwoven polypropylene landscape fabric does hold, and that is the one to buy.

Most nutsedge arrives in soil rather than on the wind. Tubers and rhizome pieces ride in topsoil and sod, so ask where the fill came from before it goes down. Shade will not save you either. Nutsedges grow poorly in shade, but a low ground cover will not shade out yellow nutsedge.

Start with the shoots you can see this week. Take out every one of them before it reaches the 5-to-6-leaf stage, then walk the same ground again every 2 to 3 weeks until the heat breaks. Each pass costs the tuber underneath. It spends 60% of its reserves on the first plant and 20% on the second, so by your third round the shoots coming up have almost nothing left behind them.

Then set the rest of the year. In spring, start looking for yellow nutsedge as soon as soil holds above 43°F (6°C), while the shoots are still small and easy to beat. In summer, hold the removal cadence, and if you spray, sedge herbicide timing decides the result more than the product does. Stay inside the 3-to-8-leaf window, before tubers begin to mature.

Fall belongs to the cause. That is the season to fix the lawn drainage, regrade the low spot, or replace the leaky head that keeps one corner wet all summer. Winter is for planning, so order the product you will need and mark the calendar to start counting leaves in late spring. A nutsedge control plan that skips the wet-soil repair just resets the same patch every year.

Be honest about the calendar too. NC State says a plan like this needs several years of sustained effort, because the tubers in your soil do not all break dormancy in the same season. And if a patch is already past the 3-to-8-leaf stage with tubers maturing, it responds poorly. No product controls mature plants well. For that season the goal is limiting new tubers, not clearing the ground.

You will not get rid of nutsedge in one summer. Dry the soil out, keep knocking the shoots down before they hit 6 leaves, and the patch gets smaller every year.