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.

A Tree-Spotter's Guide to Fruits and Seeds: Part 7

I've always been partial to pickled walnuts and the key thing to remember if you are going to pickle them is to time the harvest just right, before the coat of the developing seed inside begins to become woody, which you can test by pushing in a long needle. The soft outer fruit wall produces a black dye (which is why pickled walnuts are black) and after you've harvested them your hands go black too - it can take a couple of days for the dye to fade from your skin.

These are sitka spruce Picea sitchensis cones, which are often at the top of the tree and out of camera range, but this tree was growing on a cliff ledge and the cones were at eye level from the top of the cliff. Like so many conifers, sitka spruces are attractive trees when they are given space to develop their natural shape but all too often they are only seen crowded into dense commercial plantations. The tree a native of the west coast of North America, from Alaska to Northern California.

In comparsion to sitka spruce, the 4 cm.-long cones of giant redwood Sequoiadendron giganteum are diminutive and the seeds are minute - only about three millimetres across, including their papery wing - which is remarkable when you consider that the tree that they produce grows to a height of 100 metres and lives for over 3000 years.

The cones may be small but they do have an interesting pattern on the end of their scales........

... and are quite decorative when they ripen.

A familiar sight on the streets of the capital in winter - leafless branches of London plane Platanus x hispanica decorated with the dangling, ball-shaped fruits that break up to release small hairy seeds. The tree's only real link with London is that it's the commonest street tree there - it's actually a hybrid between Oriental plane Platanus orientalis from eastern Europe and north west Asia and the American plane (aka American sycamore) P. occidentalis. In nature the parents of the hybrid are separated by the Atlantic Ocean but they hybidised when they were grown together in Europe (possibly first in Spain - hence hispanica). The offspring of the union is a vigorous and pollution tolerant urban tree that rarely seems to be planted in the countryside.

For more on tree identification click here