The mighty redwoods

Article originally published by: Kiwi Gardener

When you mention ‘redwoods’, images of the majestic giant redwood tree come to mind. However, there are actually three species in the redwood family, all belonging to different genera. Two come from North America, and it is these which are the massive redwoods we admire so much. The third comes from China and is much smaller. All three redwoods are on the international endangered list.

Sequoiadendron giganteum, the giant redwood, is the largest living thing on the planet.

All three redwoods have become popular, worldwide, as aesthetic garden specimens, especially in large arboreta and botanic gardens where space is not an issue. Having said that, they all have a relatively thin spread, considering the extreme height they reach, but thought needs to be given to the possibility of their falling over.

Sequoiadendron giganteum, known as the giant redwood, grows on the western slopes of the Sierra Nevada mountain range in California. It gets its name by being the largest tree by volume, and largest living thing on the planet. The biggest tree of the genus (‘General Sherman’) has a volume of 1489 cubic metres, the tallest close to 95m. Trunks can have a diameter up to 17m. Recorded as one of the oldest living things on earth, ‘General Sherman’ redwoods can reach 3500 years old. Unlike their counterpart, the coast redwood, the wood of ‘General Sherman’ is said to be very brittle with little commercial value. Sadly, this did not stop many old trees from being felled even when, often, only 50 per cent of the wood was usable due to the tree shattering on impact with the ground. The leaves are small, evergreen and almost scale-like, spirally arranged on the branches.

Sequoia sempervirens or coast redwood is found in coastal forests from Northern California into far south-western Oregon. Back in the second half of the 1800s, the gold rush brought an increase in the number of people to coastal California. Unfortunately, the miners turned from gold to logging and now only 5% of the original coast redwood forests remain. Today, half of the area inhabited by the old trees (including the world’s tallest tree which stands at 115.5m) is protected in the Redwood National and State Parks.

The dawn redwood was considered extinct at one point and remains rare.

Redwood specimens in New Zealand are aged between 100 and 150 years old and are already impressive. However, considering they can live between 1200 and 1800 years in their native habitat, we have a long way to go. Being evergreen, redwoods continue to grow all year round, but their foliage catches the wind rendering trees prone to branch-drop if planted in exposed locations.

Metasequoia glyptostroboides, the dawn redwood, is so rare it was thought to be extinct until, in 1943, a Chinese forester found plants of an unknown conifer on a mountainous slope in the remote Hubei region of China. In the same year, fossil leaves were found and named Metasequoia, but it was not until 1946 that the fossils were matched with the tree to give the dawn redwood its Latin name. In 1948, the Arnold Arboretum of Harvard University funded a trip to collect seed from the remaining trees and subsequently distributed material and seed around the world for trials. Seed came to New Zealand from China in 1949, and the oldest trees in our country are now 65 years old and reaching 30m in height. Unlike its counterparts, the dawn redwood is deciduous, turning a golden brown in autumn, with lovely lime-green foliage in spring.

All three redwoods are available, but their popularity is declining due to the size they reach and the area needed to grow them. They are not a tree for the small garden but grow surprisingly well in a pot and are used extensively for bonsai. All grow rapidly when planted out but, if positioned wrongly, could well cause problems in 50 or more years.

New Zealand has some beautiful specimens of redwood trees still in their infancy, but majestic.

To locate significant other notable trees near you, check out the New Zealand Notable Trees Trust (NZNTT) website:

Coast redwood’s evergreen foliage.