Beetle infestation prompts tree removal

An arborist lowers a section of a dead tree in Duke Gardens.

By Sheon Wilson

Publications Coordinator

Crews are removing three pine trees in Duke Gardens' Culberson Asiatic Arboretum this week after detecting a virulent pest: the Southern pine beetle. 

The beetles have attacked two mature pines in Pine Clouds Mountain Stream, so arborists are removing the trees before the scourge spreads. A third vulnerable tree nearby will also be removed.

Southern pine beetle.
Photo by Marc DiGirolomo,
U.S. Forest Service

Visitors will be unable to walk through the Pine Clouds area during this work. They will be redirected with detour signs. We apologize for the inconvenience.

The work should take about three days; we will update here when it's finished. It requires taking down the trees one section at the time to avoid damaging the plants beneath. 

Southern pine beetles bore tiny holes
 into unhealthy pine trees.

During the two-year construction of the Japanese garden, which was completed in 2016, the weight of heavy equipment damaged some roots. That weakened the trees and prompted the beetles to move in. They bored tiny holes and ravaged the trees from the inside.

 “We noticed that the tops of the trees were brown; that appeared over a weekend,” said Bobby Mottern, director of horticulture. “Pine beetles are notorious for detecting trees that have been weakened.”

When pine trees are infested with Southern pine beetles,
as is the tree in the forefront, they look brown and weak.

Southern pine beetles are common, native insects. They know when a tree is stressed - by compacted soil or even drought, for instance - because the tree sends out a pheromone that the beetle detects. 

Once that happens, it’s hard to stop the beetles’ damage without fully removing the tree. Keeping trees healthy is about the only way to prevent infestations.

All photos by Sheon Wilson, except where noted.

A Festival of Fabulous Mums

By Sarah Leach Smith, Visitor Services Coordinator
Photos by Michelle Rawlins, Horticulturist

Note: This is a 2016 blog post. We hope to see you at the 2018 festival (Nov. 4-6). More info here.

Celebrate the season of chrysanthemums at the first Festival of Fabulous Mums at Duke Gardens. The mums in this display are very different from typical garden mums. You will discover an amazing array of shapes and sizes, including spectacularly large flowers with spidery petals, quill petals, pompon shapes and exotic forms, all grown for this exhibit sponsored by the Central Carolina Chrysanthemum Society (CCCS) and Duke Gardens.

This free, drop-in event will begin Sunday, Nov. 6, and run through Wednesday, Nov. 9. Festival plants will show the tremendous array of mum flower shapes, as well as the impact of different growing techniques to encourage extra-large flowers in all the autumn hues of yellow, gold, plum, rust and red.

Members of the CCCS have grown these plants just for the festival. The blooms will not be judged, as they would in a national flower show. Instead, you can vote on your favorite flowers in the display area. You will also want to tour the Culberson Asiatic Arboretum to see the exhibit-style mums throughout the landscape.

Festival activities will be in the Kirby Horton Hall in the Doris Duke Center. In addition to admiring the mums on display, you’ll be able to chat with members of the CCCS about cultivating mums in your own garden. On Sunday, Nov. 6, from 1 to 2 p.m., enjoy a floral design demonstration by Pat McCracken of McCracken’s Nursery in Zebulon, N.C., a commercial grower with a love of floral design and pottery. Pat’s completed design, which will incorporate mums and use one of his original pottery pieces, will be on display for the remainder of the festival and raffled off on the last day. There will be additional raffles as well, including a “Magic Mum Pot” that will contain everything you will need to get started in growing exhibition mums, and a beautiful chrysanthemum printed scarf from Talbots.

Children of all ages will enjoy word searches, scavenger hunts and a mum festival booklet that you can rubber stamp when you’ve seen examples of the different kinds of blooms. You will also see various forms of growing mums, such as bonsai, and displays of historical mum artifacts. Don’t miss the selfie station—you’ll be the envy of your friends on social media!

Duke Gardens horticulturist Michelle Rawlins, a CCCS member, has grown quite a number of these show mums for Duke Gardens, and those will be on display in the Asiatic Arboretum throughout November.

Michelle began growing mums for display in Duke Gardens a few years ago, and it has become a passion for her. She’s excited to host this festival with the CCCS so that we can all enjoy the demonstration of beautiful flowers trained by careful horticulturists.

You may also become captivated by the exhibit mums and want to find out even more about these amazing flowers. The CCCS is always open to new members or visitors at its monthly meetings, held on the third Monday of every month at noon at JC Raulston Arboretum in Raleigh. The society was founded in 2015 and now has more than 40 members. Michelle enjoys meeting with the group to discuss chrysanthemums and is happy to see younger generations getting more involved. “It’s like a book club, but you get to talk about your plants, how they’re growing and what challenges you might be running into."

Michelle starts her mums like this every February.

Please join us for “A Festival of Fabulous Mums” and find out what all the excitement is about. Admission is free, though parking fees apply.

The hours of this drop-in festival are as follows:
                Sunday, Nov. 6, noon – 6 p.m.
                Monday, Nov. 7, 10 a.m. – 6 p.m.
                Tuesday, Nov. 8, 10 a.m. – 6 p.m.
                Wednesday, Nov. 9, 10 a.m. – 3 p.m.

For more information, please call 919-668-1707 or email gardenseducation@duke.edu.

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.

Heat Wave! Stay Cool at Duke Gardens

The Blomquist Garden of Native Plants (gray area on the south side) and the Culberson Asiatic Arboretum (red area on the north side) are the shadiest areas of Duke Gardens.

By Sarah Leach Smith
Visitor Service Coordinator

It's that time again -- a sweltering mid-summer heat index is a daily occurrence and lower temperatures are nowhere in sight. It also happens to be an excellent time to visit Duke Gardens -- hibiscus, crape myrtle, black-eyed Susan and cardinal flower are all in full bloom.

Strawflowers in the Discovery Garden. Photo by Sue Lannon.

You can have a pleasant and comfortable experience at Duke Gardens this summer with a little bit of planning ahead. Below are some things to keep in mind before you arrive:

• Wear light-colored and loose-fitting clothing made with a natural fiber such as cotton to help you stay cool.
• Wear a hat at all times to shade your face and protect your skin from the sun. A parasol is also a good idea if you don't like wearing hats.
• Drink plenty of water -- 4 ounces for every 30 minutes outside is a good goal to aim for. Bring a water bottle with you to the Gardens and refill it at one of our water fountains outdoors or in the Doris Duke Center. See our heat advisory map for water fountain locations. 

Sun shining in the Discovery Garden. Photo by Lindsey Fleetwood.

Once you're here, it's important to orient yourself to shady spots so that you can take a break from the sun. The Blomquist Garden of Native Plants is a great choice, with thick native tree canopies that keep the temperatures lower than anywhere else in the Gardens. Another cool spot is the Culberson Asiatic Arboretum, which is also heavily covered with trees. There are benches throughout these two areas, so have a seat and enjoy the shade.

As you depart from the Gardens, we recommend that you have a "cool down plan" to help regulate your body temperature after being outside. 

When you are the Gardens or exploring other cool places this summer, keep the symptoms of heat exhaustion in your mind and be on the lookout for people who may be showing signs.

If you or another visitor are in distress, please seek assistance. If you don't have a cell phone to call 911, Duke Gardens has several emergency phones, which are marked with telephone icons on our heat advisory map. Stay safe and have a wonderful summer!

Kathleen Smith Moss Garden: A Guided Walk

Thuidium moss in the Kathleen Smith Moss Garden

Photos and text by Flora O’Brien

Mosses are growing all around us—on rocks, stream banks, shaded rooftops and trees, and emerging from the cracks in sidewalks. It’s ubiquitous, yet ever intriguing in its myriad shapes and forms. Come visit the Kathleen Smith Moss Garden in the Culberson Asiatic Arboretum and you’ll see for yourself the diversity of these primitive plants.

As you enter from the east, you’ll find a patch of Thuidium, commonly called delicate fern moss, on your right.  In the photo above, you can see its resemblance to fern. Also visible are the projections above the leaves of the plant. These are the spore-carrying reproductive bodies.

Atrichum (starburst) moss

A few steps farther along is an aged cedar stump inhabited by two species of Atrichum moss, also known as starburst moss. Continue on and there is a short dirt path on the left   leading you deeper into the garden. 

Leucobryum

Again on your left, behind the hand-carved Japanese water basin and at the base of the pine, you’ll see tufts of Leucobryum, aptly called pincushion moss (photo at left). 

Polytrichum and Thuidium

 Ahead is an outcropping of stone sheltering Climacium, palm tree moss, and a lovely vignette of Polytrichum and Thuidium mosses (photo at right).

A tableau of mosses

Back on the stone path there is a tableau of rocks and small hillocks, all loved by various mosses, lichen and liverworts. And scattered throughout the garden, you will find tufts of bluets that have emerged to greet the spring. 

As you leave, be sure to look for the tiny meadow of Hypnum moss on the left.  

Bluets signal the emerging spring.

Members of the Duke Gardens staff lovingly harvested all of these mosses locally, sustainably and with permission. Enjoy your stroll, and come back again!

Blogger Flora O’Brien is a Duke Gardens volunteer who assists in the Kathleen Smith Moss Garden.

Culberson Asiatic Arboretum: Illustrating the Relationship of Humans & Plants Across Cultures

Photo by Karen Webbink.

By Sarah Leach Smith, Visitor Services Coordinator

Paul Jones in the arboretum.

This post is the second in our series highlighting the plant collections and curators of Duke Gardens. It is thanks to them that we are a world class botanic garden!

On days when traveling to foreign lands seems unfeasible, consider a stroll through the W.L. Culberson Asiatic Arboretum at Duke Gardens. Featuring around 1,500 Asian plant species and cultivars, as well as distinctly Japanese architectural elements, the arboretum gives the sense of being on the other side of the world. Paul Jones, the founding (and current) curator of the Asiatic Arboretum, took time out recently to talk to me about this unique area of the Gardens.

The idea for the arboretum came from William Culberson, a Duke botany professor and former director of Duke Gardens. It started as a solution for one of the Gardens’ biggest challenges – flooding. In 1983, a large pond was created to alleviate the pressure of stormwater runoff from Duke Gardens and its surroundings. The 1.5-acre pond successfully contains the runoff and slowly releases excess water into a stream that carries it out of the Gardens.

Chionanthus virgincus. Photo by Jason Holmes.

Culberson decided that the area around the new pond would be an Asiatic collection, and he wanted it to serve an educational purpose. One aspect that he wanted to highlight was the disjunct distribution of plant species. Disjunct species, also known as vicariad pairs, appear to be closely related but evolved differently, because they were separated by great geographic distances after the Earth's land masses split up and shifted, forming separate continents.

North Carolina is one of the North American hotspots for North America/Asia disjuncts; 65 species native to North Carolina  have cousins in Asia. For example, fringe tree (Chionanthus) has a Chinese species (Chionanthus retusus) and an eastern North American species (Chionanthus virgincus), both of which are planted in the Asiatic Arboretum.

Chionanthus retusus. Photo by Jason Holmes.

It was at this time that horticulturist Paul Jones joined Duke Gardens as curator of the arboretum. In his initial years, Jones spent his days taking out trees and brush, opening up spaces, and improving the area around the pond. Damaged, diseased trees and invasive plants were removed to allow for new plantings. Healthy, native plants remained and were incorporated into the design of the arboretum.

In the early days, there was not much of a budget for development and plant acquisition. Jones networked with seed exchange groups and other botanic gardens to obtain seeds and seedlings to plant in the arboretum. 

“One of the most satisfying things to me is to look at some of those plants out there, which were tiny little seedlings in the 80s but now are flourishing and fruiting," Jones said. "That’s kind of cool."

The first hardscaping came in the 1990s: before then it would have been hard for visitors to tell that they were in the Asiatic Arboretum. With extremely tiny plants and no clear paths, a visitor would have to walk around to each plant tag to get any indication of a theme for the area. The construction of Asian-inspired architectural elements helped to distinguish the arboretum from the other parts of Duke Gardens.

Jones shared with me some of his landscape design philosophies for the Asiatic Arboretum. He aimed to create “rooms” in the arboretum as a way to encourage people to move around from “room to room.” He also made “windows” throughout the arboretum: openings in the landscape where you could look through and see a striking specimen off in the distance, such as a beautiful flowering tree.

The arboretum’s plant collection contains specimens that Jones collected from China, including some that are quite rare in the United States. Metapanax, a member of the Aralia family and also known as false ginseng, is one example. Jones feels that these wild-collected plants help to put the Gardens “on the map” as far as unique plant collections go. Jones has also experimented with Asian species of his favorite genus, Rhododendron, and he has found a few that have performed well in the Gardens, showing no signs of trouble with the local climate.

“I am really interested in pursuing species of plants as they might naturally occur in the wild, and what I am really drawn to as far as a landscape design philosophy is what I might find in a natural setting,” Jones said. “I don’t think that you can do better than what you find in nature.”

Pine Clouds Mountain Stream.

Jones' most recent success  is the completion of Pine Clouds Mountain Stream, a Japanese-style garden along the northwest edge of the Gardens. Pine Clouds Mountain Stream is an example of a Japanese "strolling garden," with naturalistic winding paths, water features, and thoughtful plantings.

When asked if there was one thing that he hopes visitors take away from their experience in the Asiatic Arboretum, Jones immediately responded that he hopes they will be “wowed” by the plant diversity.

What’s next for the Asiatic Arboretum? Jones would love to see more educational interpretation to demonstrate to visitors “the human community and the biological community, and how one supports the other.” He is also interested in what the arboretum has to offer in terms of teaching people about the cultures of Southeast Asian countries.

If you’re feeling in need of a getaway, look no further than the magnificent space that Jones has cultivated here at Duke Gardens. With a unique collection of plants, beautiful architectural details and a glimpse into some fascinating cultures, the Asiatic Arboretum enables visitors to feel like they're on a globe-hopping trek, while remaining in the heart of Durham.