The trees in Barcelona has name tag on the bottom. As you can see picture on the top.
It's almost impossible to refer to the landscape of Barcelona without mentioning its trees, those which stand in the parks and gardens and those planted to line avenues, squares and streets. Having had a presence on the city map since the end of the nineteenth century, they are an essential feature and are fully integrated in the city planning.
The over 151,000 trees which currently line the city's streets and avenues have become one of its most characteristic features. Sant Martí and the Eixample, with 30,788 and 22,090 trees respectively, are the districts with most trees in Barcelona. In the rest of the city -with the exception of Ciutat Vella and Gràcia, which have an urban structure that makes planting difficult- there are approximately 12,000 to 15,000 street-lining trees.
source : http://w110.bcn.cat/