Friday, October 15, 2010

A Tree-Spotter's Guide to Fruits and Seeds: Part 1

Surely the most gaudy tree in the British flora - spindle Euonymus europaeus. Spindle has been eradicated from hedgerows in some parts of the country because it acts as a winter host for the black bean aphids that infect field bean crops. That's a pity, because I can think of no other hedgerow  tree that presents such a colourful sight in autumn, when the leaves turn crimson and it produces these dangling shocking pink fruits that split open to reveal vivid orange seed. That soft orange outer layer is an aril - an extra seed coat layer that has evolved to attract birds that eat them and void the undigested hard seed seed through their gut. Arils are quite common in tropical fruits (the edible part of a lychee is an aril) but are uncommon in temperate floras.






















Catkins of silver birch Betula pendula seeds ripen in late summer and begin to break up now - as these are doing - sending down showers of tiny winged seeds. Silver birch seed is a key food source for many finches in winter, including siskins and redpolls. The seeds can be produced in vast quantities - I was recently sent some samples to identify by a train company whose trains were breaking down because of overheating caused by engine air intakes becoming blocked by seeds from lineside birch trees. 





















Indisputably a hawthorn - but which species? Common hawthorn Crataegus monogyna or Midland hawthorn C. laevigata? Now's the time to find out, by splitting open the fruit (which in botanical terns is a drupe, not a true berry). If there's one seed inside it's common hawthorn, if there are two then it's the midland hawthorn. This one had one-seeded fruits, so it's common hawthorn.

The powdery bloom on the outside of a sloe Prunus spinosa is a natural wild yeast that feeds on sugars that are produced in the fruit - although you'd be hard-pressed to detect any sweetness in the flesh of these incredibly bitter drupes. These two, and a couple of hundred others like them, are now bottled in gin in the cupboard under our stairs - and the resulting sloe gin should be ready for Christmas.

Hornbeam Carpinus betulus, famous for the hardness of its timber that was once used to make rake teeth and other similarly durable wooden items, bears these little pagodas of fruits that turn bright yellow with the foliage in autumn but remain on the tree for a while after the leaves drop, creating an effect a little like Christmas tree decorations. 

The hard seeds are nutlets, each attached to its own three-lobed bract that spins to the ground when it's released from the cluster.

For a Tree-Spotter's Guide to Buds, visit http://cabinetofcuriosities-greenfingers.blogspot.com/2009/11/tree-spotters-guide-to-buds-part-1.html

For more posts on tree ID click here

10 comments:

  1. Great post, Phil, and some fascinating facts that I wasn't aware of.

    I didn't even know of the existence of Spindle let alone ever seen one! And I'll be tearing into those hawthorn "drupes" to check for seeds. As I live in the Midlands I might just get some 2 seeders.

    One thing I do know about however is sloes, in both their raw and "processed" forms, lol.

    Pete

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  2. Fancy silver birches stopping trains! Interesting post, although I don't know any of these trees.

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  3. Great post Phil.
    There's lots of Spindle round here at the moment; those seeds really brighten up the hedgerows.
    And something else I learnt today; the Hawthorn seed, one or two. Excellent.

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  4. Excellent and informative, Phil. I'll look out for parts 2-59.

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  5. Hi Pete, thanks for your kind comments. Spindle isn't very common in the wild but it makes a very attractive small tree for a garden...

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  6. Hi lotusleaf, we sometimes have trouble with plants stopping trains here in the UK - often leaves on the line ...

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  7. Hi Keith, I have a pet theory that common hawthorn is the more frequent species here in the north because migrating birds like fieldfares and redwings feed on the berries and carry the seeds south, but when they make the return journey there are no Midland hawthorn berries left to carry north .... fanciful and probably unprovable, but plausible .... maybe

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  8. Thanks Emma, I think I might get as far as part 6... it was my brother's idea (he blogs from the Isle of Wight occasionally as Wight Rambles)

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  9. I've never seen a Spindle Tree, but as I'm in the same area as Keith, perhaps I should get out more?

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  10. Hi Toffeeapple, now's the time to spot a spindle tree - the foliage goes brilliant crimson in autumn..

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