What Age Should You Harvest?

By Piers Maclaren – source New Zealand Tree Grower, August 2003

People often ask about rotation age. How long does it take a given species to mature? Unlike pumpkins – 6 weeks, or people – 53 years, a tree is mature at any age you want it to be which is whenever you need the cash. You can produce Douglas-fir Christmas trees at age three or temple-columns at age 100. Of course, it is inefficient to fell trees too early or too late – assuming prevailing prices at the time are favourable, you maximise your profits at a certain, predictable rotation age. Let us analyse this in detail.

Peak Annual Production

When does annual volume production in a stand of radiata pine peak? It is somewhere between 20 and 30 years. Young trees are not very productive – they are too busy filling up the empty spaces between trees, and building up their green crowns. The more greenery on a tree, the more sunlight it can capture and therefore the more carbon dioxide, water and nutrients it can acquire. Eventually, all the ground-space is occupied, weeds are suppressed, and maximum crown is achieved as foliage starts to die from the bottom upwards at the same rate as it is added to the top. The stand is performing at peak capacity.

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