Yellow-grooved bamboo Phyllostachys aureosulcata.
Bamboo is a group of 1200 to 1500 species of very large and and woody grasses. I used to think of bamboo as a plant found only in Asia, especially in the tropics, but this isn't actually true. Bamboos of different species are native to parts of Africa, Australia, and the Americas, in tropical to temperate climates. Different kinds are very useful as food, building material, fibers, and as ornamental plants, and have been introduced all around the world.
I have come across three locations in Boston where bamboo has become established, there are undoubtedly others unknown to me. I probably shouldn't have been astonished at the first two encounters: growing outside the Harvard Herbaria (on either side of a chainlink fence, clearly escaped from cultivation) and in a huge stand in the Arnold Arboretum. The shock had worn off considerably when I noticed it growing all over Franklin Park Zoo. After some research, it seems most likely that the bamboo growing at the zoo is yellow-grooved bamboo Phyllostachys aureosulcata.
Yellow-grooved bamboo is native to northeast China and is one of the most cold-hardy bamboo species. It grows so well at the zoo that it requires regular cutting back, rather than nurturing maintenance. Typically plants in a given stand are 8 to 12 feet tall, with the odd twenty-footer popping up here and there. This evergreen species was originally planted to provide year-round browse for herbivores kept at the zoo, including red pandas. The plant spreads by shoots sprouting from the roots, and in Boston does not seem to flower or fruit. Wild eastern cottontails subsist well in the zoo in winter, nibbling on the lower leaves of bamboo.