Giant Redwood

*This species produces the world’s largest trees by volume. They are also amongst the tallest, growing over 80 metres at maturity. Ensure you plant far enough away from structures, well-travelled pathways and driveways, powerlines, and underground pipes. 

This forest giant is evergreen with thick, deeply furrowed, fibrous bark that surrounds a massive trunk. The crown is cylindrical to narrowly dome-shaped, made up of relatively few limbs that typically turn upwards. Some limbs are so large, that they are just as big as some fully-grown conifer species. The Giant Redwood and Coastal Redwood are often confused for each other but differ in their shape, leaf structure and appearance.

The leaves are densely and spirally arranged, awl-shaped and scalelike. The Giant Redwood has a much slower growth rate when compared to the Coastal Redwood and may only gain 10 to 20 cm growth per annum under optimal conditions.

Giant Redwoods are monoecious and will produce both pollen stomata and seed cones on the same tree. Cones will appear on some trees which are 20 to 30 years old, however, seed fertility rates are low. Sequoia trees reach sexual maturity between 200 and 250 years of age. The cones of Giant Redwoods tend to be much larger and produce seed which is flatter and paler in colour.

The wood of Giant Redwoods is odourless, light, weak and a little brittle but very decay-resistant. Giant Redwoods are somewhat fire-resistant when established and can withstand moderate fire regimes. Plants do better in temperate climates with cool to cold wet winters, and mild to warm dry summers. Giant Redwoods require quite a substantial amount of moisture from the soil, and will do better in Australian climate zones 5 to 7 and will tolerate zone 4 with adequate water supply.

Recent DNA studies confirm a close relationship between the Coastal Redwood and Dawn Redwood, based on similarities and chromosomal structures. Fossil records indicate wider dispersion compared with its current, natural range, where this tree is found exclusively in the Sierra Nevada mountains in a narrow band from Placer County to Tulare County and adjacent Fresno County.

Fossil evidence shows that Giant Redwoods were much more widespread, with deposits showing pollen, leaf imprint and petrified stumps from Europe, North America and New Zealand. Sequoioideae shows relationship evidence with Australia’s own Athrotaxis genus, suggesting that Giant Sequoia and the current Tasmanian Cedar species (Athrotaxis selaginoides, Athrotaxis cupressoides and hybrid Athrotaxis x laxifolia) share a close, ancestral lineage.

Giant Sequoias are the world’s most voluminous trees, combining their great height and diameter. Most Giant Redwoods take 200 to 300 years to reach maturity and can expect to live upwards of 3000 years. Under optimal conditions, most trees will grow to 25 to 30 metres tall and obtain a spread of 8 to 10 metres during the average human lifespan. Mature trees have been recorded more than 85 metres tall and 30 metres spread, with trunks measuring over 10 metres in diameter. Care should be taken when planting to plan for the tree’s height and circumference at maturity.

Root systems are very delicate and are prone to damage. Roots comprise fibrous white tendrils that procure nutrients and moisture from the soil. Take care when transplanting trees and ensure root disturbance is kept to a minimum. Keep in a pot until ready to plant in the ground in its permanent position. Roots extend far and can extend between 1.85 to 3.7 metres below ground and will eventually radiate outwards to support the size of the tree as it grows. Plant far enough away from concrete and asphalt surfaces as roots will uplift and damage structures.

This is best planted as an ornamental feature in a large garden, in a grove of other redwood trees, in a large field or gully. Ensure to plant in a space that can endure its presence for thousands of years.

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For more information on Giant Redwoods, see live science.