Even though they are not closely related, horsetails are grouped with ferns and club mosses as pteridophytes, vascular plants that reproduce by spores rather than seeds. Common horsetails (Equisetum arvense), as noted in my previous post, “Common Horsetail”, are dimorphic, that is, having two forms, one sterile and the other fertile.
The fertile common horsetail stems appear first in the early spring. These stems are flesh colored and succulent. The leaves are scales arranged in whorls along the stem. The spores are produced in brownish apical (at the tip) cones. Each cone consists of stalked “pads” containing sporangia (sacs) where the spores are formed. The fertile stems are non-photosynthetic.
Once the spores are formed the fertile stems wither to be replaced by the green, photosynthetic sterile stems. The sterile stems remain until fall.
The genus name, Equisetum, comes from the Latin “equus” meaning “horse” and “setum” meaning “bristle”. The Latin “arvensis” – from meadows, fields or grasslands – forms the species name.
After the eruption of Mount St. Helens in 1980, common horsetails were the first vascular plants to send up shoots.
These fertile common horsetail stems were photographed along the Lower Pit River (Shasta County CA).