Botanical name: Phyllostachys nigra ‘Bori’
Common name: Blackstem bamboo
Family name: Poaceae (Grass family)
Native range: China
Location in Duke Gardens: Culberson Asiatic Arboretum
USDA Hardiness Zones: 5-11
(November 27 update: still blooming!)
By Katherine Hale
Marketing & Communications Assistant
At more than 20 feet tall, the blackstem bamboo (Phyllostachys nigra ‘Bori’) located near the lower parking lot (see map below) has wowed visitors to the Culberson Asiatic Arboretum for decades with its attractive round culms and tree-like stature. This fall, visitors also have the opportunity to witness a rare spectacle playing out here in real time as the entire grove blooms for the first and only time in its life.
Because bamboo is so big and tree-like (not to mention impossible to mow), it’s easy to forget that it is actually a grass, right up until the moment it flowers. While individual grass flowers might not be all that showy, lacking both colorful petals and fragrant scent, bamboo flowers make up for it with both their sheer abundance and their relative rarity—a "here today, gone tomorrow" carpe diem approach to reproduction.
Unlike annual grasses, which flower every year and then die, and perennial grasses, most of which flower repeatedly over multiple years, bamboo species are monocarpic—focusing solely on vegetative growth for decades before bursting into one dramatic bloom all at once. Having spent all of its energy completely, the bamboo dies, leaving behind plenty of seeds to repopulate the area and repeat the cycle. The exact timing depends on the species, with blackstem bamboo estimated to take approximately 120 years before it flowers and dies, based on records of an earlier flowering in Japan in 1908, with additional smaller blooms reported between 1903 and 1912. Based on this calculation, the Gardens’ bamboo is a bit on the early side, heralding a larger bloom worldwide anticipated in 2028.
However, this does not mean that every bamboo culm that flowers is 120 years old—far from it. Regardless of its physical age, each culm in a grove (all of which represent a single genetic individual) will flower at the same time, an example of what botanists refer to as “mass synchronous flowering.” Although different clones within the same species may flower at different times, each clone appears to follow roughly the same internal clock, with variations due to environmental conditions between plantings.
Because it happens so infrequently, the science of mass flowering in bamboo is still poorly understood, and so much about it remains a mystery. The current theory is that it helps the plants survive by overwhelming their seed predators—similar to the mass broods of North American periodical cicadas (Magicicada spp.) that famously emerge in 13- or 17-year cycles. Many other perennial trees, including oaks and beeches, use a related strategy known as masting to alternately starve and overwhelm their predators through extreme fluctuations in seed production over multiple years.
As the blackstem bamboo here at Duke Gardens is so tall, the majority of its flowers will be higher up on the culms and may not be immediately visible from the ground. It is also unclear what impact, if any, recent bouts of cold weather will have on the overall length of the bloom period. Because this is the first time that the blackstem bamboo has flowered in the arboretum, a great deal remains unknown, with staff and horticulturists on the lookout to observe and record what happens for posterity.
Still, given that the last mass flowering here at Duke Gardens was a small grove of Japanese timber bamboo (P. bambusoides) in the early 1990s, there’s no question this is a once-in-a-lifetime opportunity for people to observe a rare and unusual botanical milestone. Say whatever else you will about bamboo, it certainly knows how to go out with a bang!
Photos from top: Blackstem bamboo culms in the Culberson Asiatic Arboretum backdropped by autumn leaves, by Karen Webbink; close-up of blackstem bamboo in flower, by Doris Duke Center Gardens curator Jason Holmes; the blackstem bamboo grove in winter, by Karen Webbink. See the map below to locate the bamboo.