Wednesday, November 30, 2011

A Tree-spotter's Guide to Conifer Cones: 1



We are in the Christmas tree season - a Baltic state and German tradition introduced into Britain by George III's queen and popularised by Queen Victoria's consort Prince Albert and  by Charles Dickens - so what better time to take a look at conifer cones?
Botanically, conifer cones are spiral whorls of scales arranged on a common axis, with each scale bearing a pair of ovules that develop into winged seeds after pollination and maturation, when the cone becomes woody, opens and releases them.





































This is Douglas fir Pseudotsuga menziesii, easily recognisable by the papery bracts, like three-pronged tongues, above each scale. Its common name commemorates David Douglas, the Scottish plant collector who in 1826 introduced this tree into cultivation. Douglas led a colourful life before coming to an unfortunate end when he was gored to death by a bull in Hawaii, at the tragically young age of 35.. The Latin specific name commemorates Archibald Menzies, another great Scottish plant collector who discovered the tree in 1792. Douglas fir is a giant tree in its native west coast of North America, where some trees may have been even taller than giant redwoods, reaching almost 400ft., before the finest trees were felled for their exceptionally fine timber. Trees introduced into Britain grew very rapidly, with some now exceeding 200ft., making them amongst the tallest trees in the British Isles. The cone is about 7cm. long.
Bearing in mind the size of a giant redwood Sequoiadendron giganteum, the tallest of all trees, its cone (above) is disappointingly small - only about 4cm. long. These trees have thick, fibrous bark that protects the living tissues below the bark from periodic forest fires, whose rising heat opens the cones and allows the winged seeds to spin down into the mineral-rich ash that they leave in their wake. The cones take two years to ripen and can stay on the tree for 20 years in their native California, though they fall much more quickly here.



We only have three native conifers here in the UK and of these only Scots pine Pinus sylvestris carries woody cones. Like many cones, those of Scots pine open when they dry, due to tensions that arise in the shrinking lignified fibres in their woody bracts, allowing the winged seeds to shake out into the breeze. The pictures above and below are of the same cone, wet and dry - a poor-man's weather glass if you keep one outside on a window ledge. This cone is 4cm. long but cone size can be quite variable in this species.




























For more posts on this blog on tree ID - buds, bark, flowers or fruits - click here.

2 comments:

  1. Do you know the legend of the Mouse and the Douglas Fir? I relate it here: http://www.flickr.com/photos/swan-scot/4702457285/

    Being in Scotland I point out that the bracts look like the Flashes worn in Highland Dress socks: http://www.kinlochanderson.com/mens/kilt-accessories/kilt-flashes

    [Working in the tourism/environmental education field, not all the information I share is purely scientific or even factual! :-) ]

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  2. Thanks for the links swanscot - fascinating!

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