21st April: Day of the Oak Tree

Today is the Day of the oak tree in the French Revolutionary Calendar. Here are 10 things you may not know about oak trees:

1. Oaks belong to the genus quercus, and there are 600 different species.
2. Oak wood is very strong and hard, and due to its high tannin content, very resistant to fungal attack and infestation by insects. Hence its use in the construction of ships, dating back to Viking times, and also for buildings and furniture.
3. This in turn has led to the oak being a symbol of strength and endurance, and being chosen as the national tree for a number of countries including England, Germany, France, Romania, Latvia, Lithuania, Poland, the USA, Wales and Bulgaria.
4. Varieties of oak have also been adopted as state tree by the US states of Iowa, Connecticut, Illinois, New Jersey, Georgia and Maryland.
5. Scientists have found that oak trees are more likely to be struck by Lightning than other trees of the same height. This is no doubt why they are sacred to the thunder gods in some mythologies - including Thor, the Norse thunder god.
6. Celtic words for the oak include derwo, doire and dru, which perhaps not surprisingly could also mean strong and firm. This gave rise to the word "Druid", the Celtic priests to whom the oak was sacred, and also the city of Derry in Northern Ireland.
7. Oak leaves and acorns are toxic to most farm animals. Cattle, sheep, Goats and Horses should be prevented from eating them as large amounts can cause kidney damage. Pigs, however, can scoff them to their hearts' content with no ill effects, and some domesticated pigs are fed exclusively on acorns.
8. You can make flour and coffee out of acorns, so presumably they aren't harmful to us, either.
9. Barrels in which Wine, sherry, and spirits such as brandy, Irish Whiskey, Scotch whisky and Bourbon whiskey are aged are made from European and American oak. Oak barrels are sometimes charred before use, and contribute to the colour, taste, and aroma of whatever is kept in them, imparting a desirable oaky vanillin flavour.
10. Individual oak trees have become important cultural symbols in some places, too. England has the Royal Oak, in which King Charles II hid from the Roundheads, and the US has the Charter Oak in which Connecticut's Royal Charter of 1662 was hidden to stop it being confiscated by the English governor-general. The oak therefore became a symbol of American independence.