Ptyxis Ecology - Our Botany Blog

Wednesday, 21 January 2009

Winter buds

One of my most memorable experiences from when I was first leaning my botany was doing a 1-day training course on winter tree identification given by Nick Bertrand. Before then I had no idea that you could use characteristics of twigs (especially the buds) to identify trees in winter. I remember getting really enthused for botany after that and I also remember enjoying showing off what I had learned to my fellow MSc students in Oxleas Wood in SE London.

Some of the characteristics that are useful are: shape of buds (rounded, pointed, conical, needle-like, etc.); number of bud scales; arrangement of buds on the twig (opposite, alternate, clustered); pattern of bud scales (opposite, herringbone, random); colour of buds (can either be very useful or very misleading!); shape of leaf scars; etc. Once you get familair with these characteristics it is fairly straightforward to identify most British species to Genus, although it is more tricky to go to species level in a couple of genera. In some ways, it is easier to identify trees in winter than at other times. Winter is a good time to do your first visit when surveying a woodland, as when the trees are naked it is much easier to assess the structural characteristic of the wood and see signs of past management. The most difficult time of year for tree identification is early spring between the time when buds start to elongate and young leaves are in the process of forming.

Here are some pictures of buds from a few species that I took yesterday down the track from our house to show some of the variety.

Ash is probably the most easily recognised tree in winter. The large terminal buds are sooty-black and conical - nothing else has buds anything like this. Note that the lateral buds are much smaller and opposite.

Willow is the only genus that has buds with only one bud scale. Lime buds looks a bit similar but have two scales. The willow buds can vary quite a bit in colour (brownish-yellow, orangey, brownish-red or purplish) on different trees of the same species, at different times of year or even on the same tree. Apart from one or two species, the others are difficult to tell apart from the buds. Most willows have alternately arranged buds.

Hawthorn have quite small buds with very small leaf scars just underneath. When I was first learning, I used to find it very difficult to tell hawthorn and blackthorn apart from their bud and twig characteristics. Now I don't have any trouble at all telling them apart as I am used to their 'jizz', but if you were to ask me to describe the key difference for identification I would stuggle to put it into words.

Oaks have clusters to tan-coloured buds at the end of the twigs with lots of bud-scales, often arranged in a herringbone pattern. Beware, that some books and keys tell you that oaks are the only genus to have terminal clusters of buds, but wild cherry often does this also. You are supposed to be able to tell the 2 British species apart by counting the number of bud-scales but I have never tested this out to be able to tell if it works or not.

Alder buds are one of the most attractive. They have a unique puple colour with a floury bloom. The lateral buds are on short stalks which is unique amongst British species.

Alder are the most decorated of British deciduous trees in winter. The old cones are unmistakable. This picture shows some tightly-closed, long males catkins with a cluster of immature female cones in the background.



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