FIELD HORSETAIL, Equisetum arvense L. 1, fertile or reproductive shoots; 2, sterile or vegetative shoots; 3, rhizomes. Perennial, reproducing by spores instead of seeds, and by rhizomes, to which are attached small tubers. Stems tough and wiry, hollow, jointed, and of two types: fertile, producing fruiting heads and having large, easily separable joints, not branched; sterile or vegetative, having much smaller joints, with lateral branches in whorls around the main stem. Leaves on sterile stems only, in the form of cup-shaped toothed sheaths at the joints. Fruiting heads contain masses of tiny pale greenish spores in small pine-cone-like structure. Found mostly on wet, sandy, or gravelly soil. It is poisonous to livestock when eaten in large quantities. There are several species of Equisetum in the area, all of which can be recognized as horsetails from this illustration.