Equisetum arvense aka Common Horsetail

Equisetum arvense, or field horsetail, belongs to the horsetail family. It is a perennial: it lives for more than one year. It grows across the Northern Hemisphere’s temperate lands and the Arctic. Its range spans Eurasia and much of North America. It is native to Britain and Ireland. It grows in fields, ditches, roadsides, and other disturbed ground. It has no flowers, fruit, or seeds.

Slim, upright shoots grow fast and form dense stands. Sources give heights of around 2–2.6 feet [0.6–0.8 metres]. Green stems have ridges and clear joints. Branches grow in rings, called whorls. The main stem is hollow; side branches are solid. Small leaves form sleeves, or sheaths, round each stem joint. These sheaths feel rough and have dark teeth along their edges. Green shoots last through summer but die with autumn frost. Black rhizomes, or underground stems, spread wide and deep. They can reach 6 feet [1.8 metres] into the soil.

Separate fertile shoots come up in early spring. They appear before the green shoots. These shorter stems are brown and white, with oval cones. The cones shed spores, not pollen or seeds. Wind blows the spores away from the plant. Small parts attached to each spore curl when wet. They straighten as they dry. This motion helps spread spores and work them into soil. The fertile stems wilt as the later green shoots grow. Most spread comes from rhizomes.

Field horsetail grows in sun or shade in many soils. These include sand, loam, clay, and chalk. It grows in acid, neutral, and alkaline soils. Moist soil suits it, but it tolerates dry or wet spells. Sources list USDA zones 3–11 and UK hardiness H7. It needs no pruning and has few pest or disease problems. Its spread is a bigger problem than its care needs. Deep rhizomes make old patches hard to remove. Dense stands can crowd other plants. RHS, though, describes it as a weaker rival. Some gardens allow it beneath mature trees and shrubs.

It gives wildlife cover and draws small mammals. Sources list its use in native gardens, natural areas, and borders. Its stems contain much silica. People have used them to scour and for fine sanding. Other uses include dyes and garden mixes that kill fungi. Several cultures have used horsetail in their folk medicine. People eat the buds in parts of Asia. PFAF lists prepared young fertile shoots and rhizomes as edible. Eating it raw is unsafe. Large amounts can harm people. Its thiaminase breaks down vitamin B1. Horses that eat it over time may grow weak and shake. Severe poisoning can cause convulsions and death.