Rough Horsetail (Equisetum hyemale) — identification, habitat & look-alikes

Rough horsetail, better known in the US as scouring rush, is a fern relative that grows on wet ground across the lower 48 states, with hollow, jointed green stems that rarely branch. Silica in the ridges makes the stems gritty, and they were once used to scrub pots and pans. It is also called winter scouring rush.

Appearance

Appearance: Stems are green, straight, and hollow, with 14–50 rough ridges. In New England plants range from about 7 in to 7 ft (18–220 cm) tall.
Leaves: The leaves are reduced to a small collar () at each joint, mostly black with a dark or thin white edge.

Look-alikes

smooth scouring rushEquisetum laevigatum

Smooth scouring rush has smooth stems and a rounded or bluntly pointed spore cone; scouring rush stems feel rough and the cone has a sharp tip.

Why they get mixed upBoth are tall, unbranched green horsetails of wet ground and roadsides.

variegated horsetailEquisetum variegatum

Variegated horsetail has only 3–12 ridges on the stem and keeps its tiny leaves at the joints; scouring rush has 14–50 ridges and its leaf tips fall off at all but the upper joints.

Why they get mixed upBoth have unbranched, jointed green stems.

field horsetailEquisetum arvense

Field horsetail has bushy green stems with whorls of thin branches, plus separate pink-to-tan unbranched spore stems that show up briefly in spring.

Why they get mixed upIts short-lived spring spore stems are unbranched and jointed.

Where it lives

Typical habitats: stream banks
lake and river shores
ditches
roadsides and railroads
Range: Native to North America and found in every state of the lower 48. Wild US plants belong to the North American subspecies (subsp. affine). In Missouri it is the most common horsetail, scattered nearly statewide. Hardy in USDA zones 4–9.
Preferred conditions: It likes moist to wet, often sandy or gravelly ground, including spots with standing water and disturbed ground, and often forms large, dense colonies.

Life cycle

Reproduction: No flowers or seeds. Spores form in a cone ½–¾ in (10–20 mm) long with a small sharp tip at the top of the stem, and even small broken bits of underground stem can grow into new plants.

Growing it

Care: Popular in modern and Asian-style gardens and water features, but it spreads aggressively by underground stems and resists herbicides, so it is best kept to wet low spots or containers.
Toxicity: Some horsetails contain , an enzyme that breaks down vitamin B1. Grazing animals may react poorly to diets high in horsetails, and eating them is not recommended for people.

Name and classification

About the name: North American plants belong to the subspecies affine (western scouringrush). Some botanists now treat them as a separate species, Equisetum praealtum.

Conservation

IUCN Red List: LCLeast ConcernLow risk of extinction

Culture and stories

Culture and stories: Musicians buy the dried stems as "Dutch rush" or "reed rush" to shape woodwind reeds.
Horsetails are often called living fossils: their relatives go back more than 350 million years, and ancient tree-sized forms helped build coal deposits.