The title of this post gives the game away but I will pose the question anyway. ‘What do Croatia, USA, Germany, UK, Cyprus, Portugal, Ireland, Poland any several other central European countries have in common?’
You got the answer ‘Oak trees as their national tree’ predominantly Pedunculate oak (Quercus robur). Portugal are slightly different having the Cork Oak (Quercus suber) as their national tree. Ireland and Wales vary the selection and opt for Sissile Oak (Quercus petraea) and Cyprus choose the Golden oak (Quercus alnifolia). Yesterday I retuned from Portugal having seen the cork oaks with the bark stripped to the pholem or inner bark layer to harvest the cork.
In this age of virus I have added a comment on a problem for Oak trees. Ramorum blight or ‘sudden oak death’ is one of the Phytophthora pathogens causing concern in UK woods and forests where it infects English oak, sessile oak, Rhododendrons and some other species of tree. It is evidenced by blackened spots on the leaf near the petiole and along the midrib of the leaf with areas of black “bleeding” on the trunk. This can lead to sudden oak death or a depletion of leaves and branches.
Xylella is a bacterium that causes leaf scorch on oak trees. Xylella fastidiosa is a range of sub species that infect a range of broadleaf plants. This pathogen prevalent in Europe and USA is transmitted by insects and is a concern for some British trees.
Do not let this stop you from growing and cherishing an Oak it will probably outlive you and several more generations. Not for nothing are Oaks venerated as National Trees by so many nations.