The Londonist website - these days the go-to place for interesting and lefty-field ideas for things to do in the capital - now features an article by Paul Wood, author of London's Street Trees, on the ten best London pubs for checking out both good beer and unusual street trees:
https://londonist.com/london/drink/10-stunning-trees-to-enjoy-in-london-while-you-re-having-a-pint