It’s fairly quiet on the flowering plant front at the moment so I have decided to look more closely at trees.
‘Everyone passes numerous trees almost every day without really seeing one of them.’ (Mitchell p31)
Mitchell goes on to describe how, by starting with looking at the familiar species and naming those, we can gain confidence in knowing what we don’t know, and eventually move further afield. This is a process that I have applied to native broadleaved trees and I like to think I’m not too bad at identifying most of them (at least to genus), even when travelling in a car or train. However I don’t think I have really given conifers much attention, probably because many of them are not native and also because they appear to be very similar at first sight. So as the saying goes ‘there is no time like the present’.
So what is a tree? Here are two definitions from noted scholars on the subject;
‘A tree may be defined as a woody, perennial plant which can attain a structure of 6m or more on a single stem. The stem may divide low down, but it must be above ground level.‘ (Mitchell p15)
So for the purposes of Mitchell’s book, hawthorn is a tree but elder is not, while hazel gets the benefit of the doubt. This aims to exclude shrubs and some climbers with woody stems.
‘A tree is a large land plant that lives for many years and forms, or tries to form a single woody stem.‘ (Edlin p22)
Edlin does however include elder and hazel in his book.
A quick trawl through the internet shows there seems to be no agreed meaning of the word tree.
Though no scientific definition exists to separate trees and shrubs, a useful definition for a tree is a woody plant having one erect perennial stem (trunk) at least three inches in diameter at a point 4-1/2 feet above the ground, a definitely formed crown of foliage, and a mature height of at least 13 feet. This definition works fine, though some trees may have more than one stem and young trees obviously don’t meet the size criteria. A shrub can then be defined as a woody plant with several perennial stems that may be erect or may lay close to the ground. It will usually have a height less than 13 feet and stems no more than about three inches in diameter.http://forestry.usu.edu/htm/treeid/what-is-a-tree-youth/
The term tree however, does not mean there is a family of trees in the way that there is a family of grasses (the Poaceae). Indeed trees are found in various plant families, so there are some in the Rosaceae but none in the Brassicaceae. Indeed trees are not just spread around in families they are in different Orders . Trees are found within the Pinopsida (which includes conifers) and the Magnoliopsida (which includes broadleaves). Unfortunately all the books I have are way out of date on classification so its difficult to know what’s what.
Anyway as far as conifer trees are concerned they are part of the Pinopsida and are all Gymnosperms which means ‘naked seeded’. However to the casual observer who looks at a pine cone, for example, they do not appear naked; because they are actually hidden within the cone.
‘If the scales of a large pine cone which is approaching maturity are prised apart, each one will be found to have two seeds developing on its upper surface. The exposure of these seeds does not involve cutting through any solid tissue, simply the separating of scales which are in close proximity with one another. In this sense the seeds may be said to be naked.’ (Simon et al, p481)
Anyway, back to Mitchell, for whom a conifer has
‘Veins parallel, not in a network, usually a resinous or aromatic scent can be obtained by crushing; usually annual growth is a whorl of branches at the base of a leading shoot often leaves dark, hard, narrow and spine tipped, rarely broad and flat; small and scale-like in many, needle like in others. Male and female flowers always separate, never with petals; fruit a cone or berry-like or green and plum-like.’ (Mitchell p33)
So there we have it, I think I’m a bit wiser, time to go and find some trees to identify!