Horsetail can grow to be 60 cm tall. It is usually 30 cm tall. Fossils from the age of the dinosaurs show it was once as much as 4 m tall. Each spike is divided into sections or segments by joints that are often brown. Horsetail can be easily broken at a joint since it is hard and very brittle when dry.
Rough ridges run up and down the stems.
There is no branching. Each stem grows singly from the roots in the ground. The tips of many spikes are swollen and dark brown. These are the spore cases which produce millions of tiny, powder-sized spores. A spore, like dust, can float on the water to new shoreline locations to start new horsetails.