What is field horsetail?

Field horsetail identification starts with recognizing that this isn’t a typical weed at all. It’s an ancient, spore-producing plant related to ferns, with no flowers and no seeds. It’s native to Pennsylvania and much of the Northern Hemisphere.

What makes it tough is underground. Horsetail grows from a network of dark rhizomes that can run several feet deep, studded with small tubers that store food. Pull or mow the top and the rhizomes simply send up more.

Horsetail is a strong sign of wet, poorly drained soil. That’s frustrating, but it’s also useful, because it points you toward the real fix.

Field horsetail identification: two kinds of stems

Field horsetail makes two different shoots, which confuses a lot of people.

• Spring spore stems: in March and April, pale tan to light brown, unbranched stems about 6 to 12 inches tall come up, each topped with a cone-like tip that releases spores. They look a bit like asparagus and wither within a few weeks.
• Summer green stems: next come the green, sterile stems, up to about 2 feet tall, with rings of thin, jointed branches at each joint. They look like little pine trees or bottlebrushes and stay until hard frost.
• Joints: stems are hollow and segmented. Tug one and it pops apart at a joint, then snaps back together like a toy.
• Texture: the stems are loaded with silica, so they feel gritty. That’s also why herbicides struggle to get in.
• Leaves: just tiny scales fused into a toothed collar at each joint.

Where it grows in Pennsylvania

You’ll find horsetail statewide in ditches, wet roadsides, stream and river banks, railroad beds and low, soggy fields. It often favors acidic, poorly drained sandy or gravelly ground in full sun, but once established, rhizomes can push into drier areas nearby.

Around homes, it shows up in the low corner where downspouts empty, along the toe of a slope, in new lawns built on poorly draining fill and in gravel areas. Central PA river-valley yards with a high water table see plenty of it. It can also arrive in loads of topsoil or fill that carry rhizome pieces.

Field horsetail look-alikes

Scouring rush is a close relative with tall, stiff, unbranched evergreen stems. It’s managed the same way. The tan spring stems of field horsetail are sometimes mistaken for asparagus or mushrooms, but the jointed sections and toothed collars give them away.

Yellow nutsedge also loves wet spots and shrugs off regular weed killers, but it has flat, glossy leaves and a solid, triangular stem. Horsetail has hollow, jointed stems and no real leaves.

How to get rid of field horsetail

Let’s be honest: horsetail is one of the hardest plants in the yard to eliminate. Realistic goals are suppression and changing the site so it can’t thrive.

• Fix the water first: because it thrives in wet soil, improving drainage is the single best long-term move. Extend downspouts, regrade so water moves away, or install a drain. Our French drain page explains how that works.
• Keep cutting it down: pulling, hoeing or mowing green stems before they reach about 8 inches, repeated through at least two seasons, slowly drains the rhizomes. Don’t rototill. Tilling chops rhizomes into pieces that each regrow.
• Thicken the lawn: horsetail needs sunlight and doesn’t compete well with dense turf, so lime acidic soil according to a soil test, fertilize and overseed.
• Beds: a thick mulch layer or landscape fabric with stone can suppress it, though shoots will find the edges.
• Herbicides: few products work well because the waxy, silica-rich stems shed spray. Halosulfuron is labeled for horsetail on some turf products, and 2,4-D or MCPA lawn products can knock back topgrowth. Expect repeat treatments and partial results.

Read and follow the herbicide label (the label is the law) and check that it’s labeled for your site, especially near ditches or streams. Applying herbicide for hire in Pennsylvania requires a PA Department of Agriculture pesticide applicator certification, so large areas should go to a licensed lawn-care or vegetation-management company.

Keeping it from coming back

Once you’ve dried the ground out and thickened the turf, keep mowing at a normal height and pull any shoots that pop up in beds. Check new topsoil and fill before you accept it, and don’t move soil from a horsetail patch elsewhere on the property.

If you keep horses or cut hay, keep horsetail out of the hay field. It’s most dangerous to livestock when it’s dried into hay.

Give it time. Rhizomes and tubers hold years of stored food, so even a well-managed patch may keep sending up thinner, weaker shoots for a couple of seasons. Each round of cutting or treatment uses up more of that reserve, and the patch shrinks steadily once the ground is drier and the grass is thicker.

Questions we get about field horsetail

Similar weeds

Yellow NutsedgeCyperus esculentusCommon Reed (Phragmites)Phragmites australisCreeping ButtercupRanunculus repens