Taxodium

Species of Taxodium occur in the southern part of the North American continent and are deciduous in the north and semi-evergreen to evergreen in the south. They are large trees, reaching 100–150 ft (30–46 m) tall and 6.5–10 ft (2–3 m) (exceptionally 36 ft or 11 m) trunk diameter. The needle-like leaves, 0.2–0.8 in (0.5–2 cm) long, are borne spirally on the shoots, twisted at the base so as to appear in two flat rows on either side of the shoot. The cones are globose, 0.8–1.4 in (2–3.5 cm) diameter, with 10–25 scales, each scale with one or two seeds; they are mature in 7–9 months after pollination, when they disintegrate to release the seeds. The male (pollen) cones are produced in pendulous racemes, and shed their pollen in early spring. Taxodium species grow cypress knees, when growing in or beside water. The function of these knees is currently a subject of ongoing research.

Species

The three extant taxa of Taxodium are treated here as distinct species, though some botanists treat them in just one or two species, with the others considered as varieties of the first described. The three are distinct in ecology, growing in different environments, but hybridise where they meet.

• †Taxodium dubium (Sternb.) Heer

Formerly placed here

• Glyptostrobus pensilis (Staunton ex D.Don) K.Koch (as T. japonicum var. heterophyllum Brongn.)
• Sequoia sempervirens (D.Don) Endl. (as T. sempervirens D.Don)