More on winter tree identification (and oaks)

The Queen Elizabeth oak in W. Sussex. It's pretty big. CC image Pam Fray

I wonder if you've heard of Nominative Determinism... there's a fair bit of it around amongst the staff of the Environmental department actually. Or maybe that's just because lots of British surnames have nature-related themes, who knows. Anyway,  here's a downloadable key to winter trees that I found this morning, to supplement others I've suggested. It's been created by Leif Bersweden (nominative determinism) of the Species Recovery Trust.

I found it via Kevin Widowson's twitter feed which itself has lots of nice photos of winter twigs at the moment. The thought that led me there was about Oaks. I was on a field trip the other day and we went to a local nature reserve that looked at first like an unprepossessing park where people walk their dogs. But actually there were some superb and huge oak trees around its edge. Old oaks are grand and noble and twisty and pretty distinctive with their very blocky bark. But if their rugged outline's not enough, they do have quite an unusual arrangement of buds. As I looked up at the twigs silhouetted against the grey February sky I could easily see the buds were in clusters at the ends of the twigs.

I also found a superb resource from the EU Science Hub Forest project, The European Atlas of Forest Tree Species. It has lots of interesting information on the ecology, habitats and cultural importance of many species (i.e. things you might even want to mention in your notebook). Also, you can make some taxonomically-relevant comparisons - I was reading about goat willow (Salix capraea) and it compares the different soil moisture / light preferences etc. of different willows.

There are also pages about the two native oaks in the UK, the English oak (Quercus robur) and the Sessile oak (Quercus petraea). For some reason I've never been able to get all the names and features of the two species straight in my mind. So here is my attempt to. It sounds like they should be readily distinguishable even in winter when the usual things you'd check (the leaves and acorns) are not about.

Quercus robur (CC Sten)

Quercus petraea (CC Sten)

Quercus robur                                      Quercus petraea
aka English oak                                    aka Durmast oak ('mast'=acorns)
aka Pedunculate oak                             aka Sessile oak

buds are ovoid                                      buds are pointy
buds are hairless (although                  buds have long white hairs
  may have fringey edges)
buds are said to have less                     buds are said to have more
  than 20 scales                                       than 20 scales


'Pedunculate' and 'Sessile' are words meaning 'stalked' and 'stalkless' respectively. But my problem has always been to remember to what they refer.
Q. robur  has pedunculate (long stalked) acorns, but (confusingly to me) a short stalk to its leaves.
Q. petraea has sessile (stalkless) acorns, but a long stalk to its leaves.
You might think this is a bit of an academic point in the winter, but it's always worth a look in the leaf litter for clues.

It's also said that Q. robur has blunter-tipped acorns than Q. petraea. And I've read different colours for the descriptions of the twigs. But colour always seems a bit too subjective to me, especially if you've only got one specimen in front of you. It's more the sort of thing you get a 'feel' for as part of the overall character of the species, that you might notice once you've seen and examined quite a few trees.

Their outlines, due to their way of growing, can also differ - Q. robur supposedly spreading out with irregular twisting branches and the main trunk still large and visible in the crown, whereas Q. petraea is ideally more orderly with a straight main stem and straighter branches in sensible size order. Of course, their appearance will depend on not least where they're growing - on their own or amongst lots of trees in a forest. And their age. So I don't think it's entirely clear cut.

Quercus robur, being the arboreal symbol of England, is, unsurprisingly, found in the lowlands of England. Quercus petraea is native to the oak woods of Western Britain. So you should probably be on the look-out for both. Also, to confuse matters (as ever), the two are quite variable and can even hybridise, producing trees with intermediate characteristics. Thanks a lot, trees. People are determined to pigeonhole everything into separate categories. But you confound us.

Oak leaves and flowers (male catkins) emerge from the buds. CC image Kenraiz