I got to visit three botanical gardens this summer when I was in Europe: Berlin Botanical Garden, Oxford University Botanical Garden, and Kew Gardens - the Royal Botanical Garden in London, UK. Great fun to see North American plant species in their collections. Kew had a black locust tree that had been planted in the 1700s along with a whole grove of redwoods and sequoias! Berlin Botanical Garden had a collection of Hydrocotyle bonariensis growing in one of their greenhouses!
Berlin Botanical Garden:
Kew Gardens in London:
Giant black locust from the North America planted in Kew in the 1700s!
Oxford University Botanical Garden: