A small patch of Giant Horsetail (Equisetum telmatiea) emerges from a moist gully alongside Salmon Creek in the Willamette National Forest. The Giant Horsetail is a herbaceous perennial which reproduces both by spores and expansion of its rhizome. Often they are found growing in large dense colonies; with shoots growing to 150 cm, and occasionally reaching heights of up to 240 cm.
In this photograph, all of the shoots save one are non-photosynthetic and are used for reproduction. These are the pale spore-bearing stems which lack chlorophyll and have a bulbous [strobilus] at their apex.
The smallest shoot in the foreground which is slender, pointy and developing a blush of green chlorophyll is sterile, and will be tasked with light gathering energy production for the mass of rhizomes safely buried beneath the surface at depths up to four meters.
The Giant Horsetail is one of 25 species of horsetails and scouring rushes which comprise the genus Equisetum. These are the hardy survivors of what was once a vast number of species within this genus at the height of their reign over 300 million years ago in the age of the Carboniferous swamp forests. At that time members of this genus could obtain heights of 20 meters, and are today well represented in the Carboniferous fossil record.