Kingdom: Plantae
Division: Pinophyta
Class: Pinopsida
Order: Pinales
Family: Cupressaceae
Subfamily: Sequoioideae
Genus: Sequoiadendron
Species: S. giganteum
Binomial name: Sequoiadendron giganteum
Synonyms: Wellingtonia gigantea, Washingtonia californica
Common names: Giant sequoia, Giant redwood, Sierra redwood, Sierran redwood, Wellingtonia redwood, Big tree, Sequoia.
Sequoiadendron giganteum is world-renowned as the largest living thing on the planet. It is the sole living species in the genus Sequoiadendron, and one of three species of coniferous trees known as redwoods. Sequoiadendron giganteum occurs naturally only in groves on the western slopes of the Sierra Nevada Mountains of california.Sequoiadendron giganteum are the world's largest trees by volume. They grow to an average height of 50–85 m and 6–8 m in diameter. Record trees have been measured to be 94.8 m in height and over 17 m in diameter. The oldest known giant sequoia based on ring count is 3,500 years old. Sequoia bark is fibrous, furrowed, and may be 90 cm thick at the base of the columnar trunk. This bark is nearly resistant to fire because it is non-resinous.
The small, evergreen, scale-like leaves are green 3–6 mm long, and arranged spirally on the shoots.
Both male and female cones are carried on the same tree; female cones are up to 7.5 centimetres long and four centimetres wide. They are reddish-brown when mature and contain numerous flattened winged seeds.
The seed cones mature in 18–20 months, though they typically remain green and closed for up to 20 years; each cone has 30-50 spirally arranged scales, with several seeds on each scale, giving an average of 230 seeds per cone. The seed is dark brown, 4–5 mm long and 1 mm broad, with a 1-mm wide, yellow-brown wing along each side. Some seeds are shed when the cone scales shrink during hot weather in late summer, but most are liberated when the cone dries from fire heat or is damaged by insects.
The giant sequoia regenerates by seed. Trees up to about 20 years old may produce stump sprouts subsequent to injury. Giant sequoias of all ages may sprout from their boles when old branches are lost to fire or breakage, but (unlike coast redwood); mature trees do not sprout from cut stumps. Young trees start to bear cones at the age of 12 years.
At any given time, a large tree may be expected to have about 11,000 cones. The upper part of the crown of any mature giant sequoia invariably produces a greater abundance of cones than its lower portions. A mature giant sequoia has been estimated to disperse from 300,000-400,000 seeds per year. The winged seeds may be carried up to 180 m from the parent tree.
Lower branches die fairly readily from shading, but trees less than 100 years old retain most of their dead branches. Trunks of mature trees in groves are generally free of branches to a height of 20–50 m, but solitary trees will retain low branches.
Photographed at Botanical Gardens, Christchurch.
The trunk of the above tree.
One of two giant sequoia listed as NZ notable trees in Nelson Park. Picton.
http://register.notabletrees.org.nz/tree/view/333
Two younger trees at Blenheim racecourse with the typical pyramidal shape
The scale-like leaves.
The small cones of Sequoiadendron giganteum.
