Equisetum species, also known by multiple names including horsetails, scouring rushes, candock, puzzlegrass and snake grass, is a family of ancient vascular plants. These primitive plants have rhizomes, underground stems, as well as above ground stems, and show a close relationship to ferns. The vascular ability implies that Equisetum species have conducting systems that transport nutrients and water throughout the plant, providing the necessary resources as they are required. The name Equisetum arises from the fact that the branched species of this family look similar to a horse’s tail, and so Equisetum derives from the Latin words, equus (horse) and seta (bristle). Equisetum is the sole surviving genus of a complex group of primitive plants which covered the planet during the Carboniferous period more than 300 million years ago, and scientists find it difficult to distinguish modern day Equisetum species from the small of plants of that period, suggesting that very little evolutionary changes of this genus have occurred over time.
There are currently around 20 species of Equisetum, distributed around the world, with many species found in Asia and Europe. These plants typically grow in wet places such as ponds, marshes, wet woodland and the banks of lakes and rivers. They are also able to survive in drier areas where their deep running rhizomes underground can reach moisture.
It is quite simple to identify Equisetum species based on their features, or lack thereof. The leaves occur in whorls. They fuse into a sheath at the stem joints, and are very small in size, so small that they appear to possibly have minimal function. They are usually non-photosynthetic. Food is produced via photosynthesis in the stems and branches of the plant, although the branches are mostly absent, depending on the species of Equisetum.
One of the key features of Equisetum species is the stem. These stems are upright, hollow, and cylindrical. They are jointed in appearance, with ridged surfaces along the longitudinal plane. Stems arise at close intervals from long underground rhizomes, sometimes forming colonies. Cones are found at the tips of fertile stems and contain sporangiophores bearing sporangia which hold spores. Spores are single-celled units that are capable of reproduction and so enable these plants are able to produce the next generation. When the sporangia are mature, they open up and in doing so, release the spores. These tiny, green spores are dispersed into the wind, and since they are extremely light, the spores can be carried large distances until they are able to produce the next generation. The plants are primarily distinguished from each other by the presence or absence of branching, presence of leaves, number of leaves, color of leaves and general habitat. The type of environment in the habitat affects the type of branching as well as height and general appearance of these plants, to the degree where even individual plants closely located to each other differ from each other.
These plants are regarded as weeds, and are known to be toxic to a number of animals, including horses, cattle and sheep. They also reduce crop yields by producing substances that inhibit the growth of plants around them. Equisetum also apparently has some benefits in the medical world, but is to be used with caution due to the associated toxicity in the aforementioned animals.