Spain is a country that is located in South west Europe. It is a kingdom which has Mediterranean Sea, Gibraltar, France, Andorra, Bay of Biscay, Portugal and Atlantic Ocean in his immediate neighborhood.
Spain is a democratic country that has a parliamentary democracy and also a Constitutional Monarchy. I did a lot of research on your question and have come to the conclusion that Spain might not have a national tree after all. As it is not mentioned anywhere. However there are many trees that have regional importance in Spain like Madrono tree, Pinsapo Tree, Oak Tree, Holm Oak, Drago etc.