Plant 263

Sequoia sempervirens (D.Don) Endl. (Cupressaceae)

California redwood

California redwoods are the world's tallest trees. With heights of more than 110 metres and trunk diameters greater than six metres, these enormous organisms form a distinctive forest type along the Pacific coast of the North America between southwest Oregon and California. Individual California redwoods are known to live for thousands of years, and can exploit sea mist as their major water source.

The region where the California redwood grows is subject to periodic disturbances, especially fire. Trees are adapted to such conditions by having thick, fibrous, fire-resistant bark, the absence of flammable resins and the ability to resprout readily. Individual trees respout at all levels from apex to base. Under the soil surface, trees have massive, woody structures containing large numbers of buds and high levels of food reserves. If the main stem is damaged, new shoots readily form from these buds.

The closest living relatives of California redwood are North American giant sequoia (Sequoiadendron giganteum) and Chinese dawn redwood (Metasequoia glyptostroboides). Detailed investigations of these three species' DNAs have led to the intriguing suggestion that California redwood arose as the result of ancient hybridisation between the ancestors of Sequoiadendron and Metasequoia.

California redwood was first described by the Scottish botanist David Don, based on a specimen collected by his countryman Archibald Menzies during the Vancouver Expedition (1791-1795). However, Don was uncertain about his description; it was based on 'only a single imperfect specimen' but it was 'too interesting to omit' from Aylmer Lambert's A description of the genus Pinus (1803-1824). Don left it 'to future observation to determine, whether or not the place I have assigned to it be correct'.

When the California redwood was first given its scientific name it was placed in the same genus as the deciduous swamp cypress (Taxodium), and given the species epithet sempervirens to emphasise that it was evergreen. In 1847, the Austrian botanist Stephen Endlicher thought the California redwood distinct enough to give it its own genus. The name he chose, Sequoia, appears to have been used to commemorate the Cherokee Sequoya (c.1770-1843), who invented the Cherokee writing system.

California redwood is a rapidly growing species that has found favour as an ornamental in large parks and gardens outside of its native range. Within its native range, the timber of California redwood has been used where resistance to decay is a premium quality, e.g., roof shingles, railway sleeepers and bridge supports.

Further reading

Farjon A 2010. A handbook of the world's conifers. Brill.

Muleady-Mecham, NE 2017. Endlicher and Sequoia: determination of the etymological origin of the taxon Sequoia. Bulletin of the Southern California Academy of Sciences 116: 137-146.

Yang ZY et al. 2012. Three genome-based phylogeny of Cupressaceae s.l. : further evidence for the evolution of gymnosperms and southern hemisphere biogeography. Molecular Phylogenetics and Evolution 64: 452-470.

Stephen Harris