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