Common Plant Characteristics in the Horsetail Family

Physical Characteristics

• Horsetails have hollow, ridged stems joined by joints. Plants can grow up to 24 feet tall but most are just a few feet tall. They develop a sterile, vegetative stem that holds foliage and is usually green, and a shorter, reproductive stem that generally grows in shades of brown or tan and holds cones. Horsetails have very small foliage, usually less than an inch long, that resemble needles. Their whorled, scale-like leaves emerge from nodes, with up to 40 leaves growing from a single node. Horsetails have a deep, creeping system of rhizomes, or underground stems that grow laterally and produce other stems and rootlets. They can be perennial (living for many years) or annual (living for a single growing season).

Reproduction

• Like ferns, and unlike most other members of the plant kingdom, horsetails spread by spores rather than by through flowers and seeds. Horsetails produce brown stalks topped by cone-like structures that house their spores. Horsetail spores are spherical, homogenous in size and have four to six elaters, or structures that eject the spores from cones. When humidity decreases, the elaters spring open and eject the spores into the air. Rhizomes also regenerate if cut into small pieces.

Habitat

• Horsetails prefer moist soil such as found on lakeshores, near ponds and rivers, in wetlands and in boggy areas. In the U.S., they naturally grow in every state except Florida and Louisiana. While most species prefer wet to moist soils, some tolerate drier sites and will colonize in orchards, pastures and along roadsides. Certain varieties are toxic to wildlife and many types are herbicide-resistant. Horsetails can be difficult to eradicate due to their deep rhizomes.

Common Types

• Some horsetails are cultivated as ornamentals, but most grow wild. Some are even considered pests or weeds. Cultivated varieties include scouring rush or rough horsetail (Equisetum hyemale), which grows in an upright form and is used as an ornamental plants in water gardens or in containers. Scouring rush spreads invasively if left untended. Field horsetail (E. arvense) grows from 1 1/2 to 2 feet tall and has green sterile stems with narrow, bright green foliage that grows from each joint and a flesh-colored reproductive stem. It prefers wet environments. Smooth scouring rush (E. laevigatum) has abrasive, evergreen stems with dark stripes at the joints. It grows in wet to dry soils.