[2][3] It was formerly widely treated in a broader sense including a subspecies (subsp.

The sterile stems, produced in late spring and dying down in late autumn, are 30–150 cm (12–59 in) (rarely to 240 cm (94 in)) tall (the tallest species of horsetail outside of tropical regions) and 1 cm (0.39 in) diameter, heavily branched, with whorls of 14–40 branches, these up to 20 cm (7.9 in) long, 1–2 mm (3⁄64–5⁄64 in) diameter and unbranched, emerging from the axils of a ring of bracts; the main stem itself is whitish, without chlorophyll or stomata.

[6] Occasionally plants produce stems that are both fertile and photosynthetic.

[9] Its southern and eastern limits are less well mapped, but it occurs south to Madeira (32°45' N), the Atlas Mountains in northwest Africa, and Israel, and east to Iran;[4] the easternmost mapped on iNaturalist ('research grade' records only) is at 52°58' E in Iran.

[10] It is found in damp shady places, spring fens and seepage lines, usually in open woodlands, commonly forming large clonal colonies.