Tuesday, September 13, 2016

Bamboo at Duke Gardens: Friend or Foe?

Winter view of yellow bamboo (Phyllostachys 'Robert Young'). Photo by Rick Fisher.

By Sarah Leach Smith, Visitor Services Coordinator
With help from Beth Hall, Plant Collections Manager

Bamboo restoration by the Arched Bridge. Photo by S.L. Smith
For most homeowners, bamboo is perceived as an annoyance. The general consensus is that it spreads aggressively, it’s impossible to control and it can be destructive. Many people wonder why it’s planted at Duke Gardens and why it’s roped off and protected as part of a “bamboo restoration project.”

Paul Jones, curator of the Culberson Asiatic Arboretum at Duke Gardens, has incorporated bamboo into the arboretum's design for decades, and he uses it purposefully and artfully.

The Gardens' bamboo collection contains what Paul refers to as the “trifecta” – large species, short species and clumpers. Large species, such as the black-stemmed bamboo (Phyllostachys nigra), can get as tall as 35 feet. Shorter species in our collection include those that reach a maximum height of 6 feet, such as the Kuma bamboo grass (Sasa veitchii). Clumping species have gotten popular lately because they don’t spread as quickly; they form close-knit “clumps” rather than growing out and away. One of the clumpers in our collection is Green Panda™ bamboo (Fargesia ‘Rufa’ Green Panda™), which typically reaches a maximum height of 10 feet.  In total, the Duke Gardens bamboo collection contains 24 different species.

A young bamboo shoot that has been damaged.
Photo by S.L. Smith.
How does Duke Gardens control its bamboo, given its bad reputation for spreading exponentially? We don't, Paul says with a laugh. We can exert some control on the part growing above the ground, but the roots continue to spread. Bamboo makes new shoots once a year in the spring, and the shoots are fragile when young. Breaking them off in that early stage causes the new shoots to die back, but the roots stay alive beneath the soil. This robust root system can prove challenging, especially if Paul and his team want to plant things near the bamboo. Digging through the roots is tough!

However, Paul hesitates to refer to bamboo as an "exotic invasive," as some people do. That designation is best applied to non-native species that spread by running or vining agressively, by wind or water, or by producing seed that is consumed and transported by birds and other animals. Because bamboo very rarely flowers and goes to seed – many only flower once every 80 to 125 years – its spreading is very localized and it is simply an ever-increasing clump. It doesn’t spread nearly as fast as some of the most invasive plant species in our area, such as Japanese honeysuckle (Lonicera japonica), callery pear (Pyrus calleryana) and Chinese wisteria (Wisteria sinensis).

Cutting unwanted new shoots helps prevent spreading above 
ground. Photo by S.L. Smith.
“There are so many things you can do with bamboo. It’s a great building material and a delectable food source for people and animals,” he adds. For example, at Duke Gardens we use our bamboo to create handrails and "wickets" to edge plant beds.

As it turns out, when you actually want bamboo in a garden, there are some that present challenges. “One of my goals early on was to establish a grove of Japanese timber bamboo (Phyllostachys bambusoides) that would take up maybe 1/8 of an acre with a path going through it," Paul says. "It’s a very surreal and beautiful type of landscape environment.”

Pretty soon after planting the Japanese timber bamboo, though, Paul learned that the squirrels in the Gardens loved eating the young shoots. Additionally, foot traffic through the planted area caused a lot of damage to the bamboo and ultimately led to the area being closed off to visitors. Now, every spring and through the summer, there are several stands of different bamboo species that get roped off and a “Bamboo restoration in progress" sign is posted to deter people from walking through and harming the young shoots. The Japanese timber species is the only bamboo that has actually flowered at Duke Gardens, and remnants of the original planting still remain in the Asiatic Arboretum.

Engraving in the bamboo. Photos by S.L. Smith.
Along with discouraging people from walking through the young bamboo, the ropes also discourage people from engraving the bamboo, an impulse that it's critical to curb.

“For one thing, it suggests that it’s OK to carve on plants in the Gardens," Paul says. "Even if it’s just the bamboo, it then suggests that it’s OK for that beech tree over there to be carved, and that it’s OK for that bench to be carved on, too. Would you go into an art museum and carve your initials into the frame of a fine art piece? Carving is graffiti, whether it’s a plant or a bench or a frame." 

Engraving is also harmful to plant health. In some cases, there is so much carving on a bamboo cane or tree trunk that the damage goes all the way around. When this happens, the vascular system of the plant is harmed, which prevents water and nutrients from traveling throughout the plant. This weakens and can ultimately kill it. As a botanic garden, we want to protect plants from this sort of preventable tragedy. 

But bamboo can be amazingly strong, too, Paul notes. One of the coolest examples he had seen was its use as scaffolding to construct high-rise buildings in the south of China when he visited in the early '90s. Bamboo has a tensile strength competitive with steel.

Please help us preserve this unique plant collection for generations to come. Watch your feet for young bamboo shoots emerging in the Gardens and refrain from carving into the bamboo. If you have further questions about bamboo or any of the other intriguing plants in the Asiatic Arboretum, we hope you'll seek out one of our staff members or volunteers. We would be happy to share more about Duke Gardens' many delights.

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