Charlotte Kingan, of Ardgowan School, asks :-

What is the biggest tree in the world?

John Walker, of the School of Forestry, University of Canterbury, responded.

You have to go to the United States of America to see a real world-beater in the Coast Redwoods (Sequoia sempervirens) and Giant Sequoias (Sequoiadendron giganteum) of California and Oregon.

According to Hugh Johnson (The International Book of Trees, publ. Mitchell Beazley Ltd., London 1973) the tallest redwood is 112 metres.

Johnson provides the flavour for size "It took even 19th-Century Californians in all their vigour and rapacity quite a time to think of a way of cutting down such formidable creatures. There is a note of hysterical triumph in the account of five men working for three weeks boring holes round the trunk of a tree (30 metres) in circumference to fell it. It never occurred to them to leave it where it stood."

Why so tall? The coastal redwoods capture much of their moisture from coastal fogs - so maybe they need a large sail area? The giant redwoods are in the Sierras and get much of their moisture from snow melt. It is hard to find a common explanation! They are both low-density trees (intermediate between balsa and Douglas fir) so their bulk belies their more moderate biomass which is an efficient way of achieving height while retaining stiffness and strength. Their sap-conducting capillaries are much wider than most species so they have 'arterial plumbing' rather than the local reticulation. Why so tall? In truth, I don't really know!

For noteable trees in your area consult the Forest Research Institute in Rotorua's series of five regional booklets by S. W. Burstall on "Historic and Notable Trees of New Zealand". Your local library should hold the copy for your area.