Although the box tree moth (Cydalima perspectalis) has not yet arrived in the U.S., the pest is not far away. The pest is native to eastern Asia, and was detected in Toronto, Canada, in 2018 and is prevalent throughout Europe.
Based on DNA evidence, box tree moths were introduced into Europe from Asia multiple times and moved within Europe via nursery trade after they were introduced. Once the moths got onto wild European boxwoods, they were able to spread relatively unchecked.
Sources: Penn State Extension, Canadian Food Inspection Agency, Horticultural Research Institute
Southern Nursery Association to cease operation
Departments - View Point
Citing declining membership and the 2021 cancellation of its conference, the 121-year-old organization is coming to an end.
At the end of January, I was saddened to learn that the Southern Nursery Association (SNA) board of directors voted unanimously to shutter the organization. Because of the continued strain on travel from the coronavirus, SNA was unable to host its 2021 conference, its main source of income.
Founded in 1899, SNA’s mission was “to unite and advance the horticulture industry through educational, research and marketing efforts.”
SNA produced a robust trade show from 1950 – 2009, the SNA Research Conference from 1955 to 2020, and the SNA Plant Conference from 1991 to 2020. The association also produced The Best Management Practices Guide in 1996 with updates in 2007 and 2013.
Some of the research that came out of the SNA Research Conference was groundbreaking, and thankfully the library of more than 3,000 titles will eventually be housed on the Horticultural Research Institute (HRI) website (www.hriresearch.org).
SNA Executive Vice President Karen Summers says the board is exploring other avenues with AmericanHort to help preserve the research conference, the student competition, and the BMP Guide.
To help preserve SNA’s 121-year legacy, two existing HRI funds (the SNA Fund and the SNA Golf Classic Fund) will be combined — totaling some $300,000 — and renamed the Southern Nursery Association Legacy Fund. These funds are earmarked for horticultural research in the southeast region of the U.S.
The organization’s impact on horticulture students is immense. And I was relieved to hear that the Sidney B. Meadows Scholarship Endowment Fund (www.sbmsef.org) will not be impacted. It’s a non-profit 501(c)(3) charitable corporation fully independent of SNA and will continue to award academic scholarships to horticulture students throughout the southeastern U.S. To date, the fund has awarded more than $550,000 in scholarships. The fund balance currently stands at more than $900,000.
I’d like to tip my hat to Karen and Danny Summers, who have worked tirelessly to promote and expand SNA. I know this was a heartbreaking decision for them and the board.
When an organization like SNA has been around for more than a century, its closure will have a ripple effect on the industry. We must not take things like research and scholarships for granted. Our local, state, regional and national organizations need our support to maintain the assistance and benefits they provide the industry. In this new and likely unconventional year, consider volunteering your time and becoming a dues-paying member to a nearby association. Let’s keep the legacy of SNA alive.
Departments - Green Guide
This evergreen groundcover received the esteemed Award of Garden Merit.
I recently watched the movie “Fletch” for the umpteenth time. One of the things that makes me laugh is all the aliases Irwin Fletcher invented during the course of his undercover investigation. Saxifraga stolonifera has an impressive array of pseudonyms as well, from strawberry geranium and strawberry begonia — it is neither a begonia or a geranium — to creeping rockfoil and roving sailor, and a few more. Whatever you want to call it, Saxifraga stolonifera is a fabulous garden plant for light to moderate shade. As its name implies, it spreads by creeping stolons much like a strawberry and its leaves are shaped similar to a geranium or begonia. It’s easy to see why gardeners have called it strawberry geranium or strawberry begonia. It forms a dense groundcover and sports showy white flowers on 18-inch stems from late spring through mid-summer. The foliage is evergreen, and quite eye-catching. The undersides of the leaves are a dark pink-red color and add to the plants allure. There are a few notable varieties available in horticulture. ‘Hsitou Silver’ collected from the Hsitou region of Taiwan has beautiful silvery foliage, and there is a nice, variegated form marketed as ‘Tricolor’.
Saxifraga stolonifera is native to China, Taiwan, Japan and the Korean peninsula. It grows in humus rich, well-drained soils in partial to full shade. It received the prestigious Award of Garden Merit from the Royal Horticultural Society. S. stolonifera is a great shade groundcover in the landscape and is also a fabulous container plant. It’s relatively easy to grow in nursery production, as well as in the garden. Damage from disease or insects is rare. You won’t regret adding Saxifraga stolonifera to your production plan or to your garden.
Why grow Saxifraga stolonifera?
It’s a great evergreen shade groundcover.
Its attractive leaves are beautiful in the landscape.
Its showy white flowers are attractive to pollinators.
It’s a wonderful container plant either alone or mixed with other plants.
Mark Leichty is the Director of Business Development at Little Prince of Oregon Nursery near Portland. He is a certified plant geek who enjoys visiting beautiful gardens and garden centers searching for rare and unique plants to satisfy his plant lust. firstname.lastname@example.org
Work of art
Features - Cover Story
Hydrangeas are always on exhibit at the Heritage Museums and Gardens.
Cape Cod is home to many a hydrangeaphile. Landscapes in this historic and idyllic area of southern New England are adorned with some spectacular specimens. The Cape Cod Hydrangea Society is a lively and generous organization that has been educating the region about hydrangeas, what they call “the signature flower of the Cape.” And Heritage Museums and Gardens in Sandwich, Massachusetts dedicate an impressive number of man hours and space to hydrangeas throughout the grounds, including a display garden and a test garden.
Mal Condon is the curator of hydrangeas at Heritage. He’s been propagating and growing hydrangeas for 45 years. It only takes a few minutes chatting with Condon to realize he’s brimming with hydrangea knowledge and his love of this crop is genuine. With all of this ballyhoo surrounding hydrangeas, Cape Cod is a mecca of sorts for a crop that’s become quite valuable to the green industry.
“Hydrangeas are the No. 2 shrub behind roses, and I think they are so popular because of the magnificent flower,” Condon says. “With different species, you can have sequentially blooming shrubs and a summer full of hydrangea blooms. They are plants that home gardeners can handle very well and they get a lot of enjoyment from. I don’t see that changing.”
At Heritage, the hydrangea display garden came first. With nearly 2 acres, the display garden is a joint effort between the Cape Cod Hydrangea Society and the museum. Initial planting began in 2008 and continued through 2010 with relocations and expansions in 2012, 2013 and 2014. The display garden is home to eight hydrangea species and more than 160 cultivars. It’s maintained almost exclusively by the society.
“The display garden is made up most of macrophyllas, but we have a decent amount of paniculatas and serratas, as well,” Condon says. “We also have a lot of legacy varieties that aren’t typically available in the trade. I’m trying to locate some of the old arborescens cultivars.”
An idea takes shape
The test garden was the brainchild of Dr. Michael Dirr, whose hydrangea selections and breeding helped catapult the crop’s popularity. Dirr brought up the idea during the 2015 Hydrangea Conference at Heritage and before the end of the event, a plan was in place to move forward. Dirr, Bailey Nurseries, Star Roses & Plants, the American Hydrangea Society and the Cape Cod Hydrangea Society committed $100,000 total to initiate the test garden.
“I helped Heritage chase grants and asked people like Mark Sellew at Prides Corner, Tim Wood at Spring Meadow, Greenleaf and others for plant donations, and all responded positively,” Dirr recalls.
The test garden’s mission is to trial the newest hydrangea introductions across the species spectrum and report on performance, Dirr says. But there are some “old standards” included in the design for performance comparisons, Condon adds.
The North American Hydrangea Test Garden
Les Lutz, horticulture director at Heritage, designed the test garden, which includes sun and shade conditions for the hydrangeas, as well as hardscapes, water features and complementary perennials, shrubs and trees.
“Les created a beautifully designed garden that’s horticulturally rich and integrated with all manner of plants, no just test rows with ugly signage,” Dirr says. “The casual visitor would have to sleepwalk through the garden and not come away with new ideas.”
The test garden opened in the summer of 2016 with the goal of becoming the most comprehensive collection of the genus in the U.S., Condon says. As of June of 2020, there were 244 hydrangeas under evaluation, including: H. arborescens (35 plants and eight cultivars); H. macrophylla (136 plants and 21 cultivars);
H. paniculata (67 plants and 11 cultivars); and H. serrata: (three plants and 1 cultivar).
There’s a heavy emphasis on H. macrophylla in the test garden because it makes up the majority of commercial production.
“The macs are superb — they’re always tough and they have great texture and color diversity,” Condon says. “We talk a lot about the macrophyllas, but paniculatas and arborescens are bulletproof. They’re my favorites, and once established, they do so well for us.”
The macrophyllas are evaluated for their winter/bud hardiness, reblooming capability, bloom density, bloom quality, general growth and size characteristics, sun tolerance, and pest and disease pressure.
There is a lot of focus on reblooming capability at the test garden because the market puts a lot of emphasis on that characteristic. All stem tips are pinched in July — an action Condon calls their “most critical test” — to evaluate the number of new inflorescences that develop by late August and into September.
The test garden is located in USDA Hardiness Zone 6a, while the rest of the Cape is 7a. Soil prep is a critical step at the gardens where the soils are a glacial marine composition with stone, sand and clay veins, Condon says.
“We blend on-site produced compost with our inherent glaciated soil. In worse cases we screen the latter to remove the sometime major rubble content,” he explains.
Pruning is a two-step practice in late winter and early spring.
“Aging canes are removed first for regenerative pruning in March and early April. All vibrant wood is left until detail pruning is done in May when the failed upper stem wood is removed,” he says. “This seasonal pruning approach has sustained a very high percentage of vital wood while also maximizing flower bud development.”
Plants are not treated with insecticides or fungicides once they’re in the ground.
Condon’s crew applies a controlled-release fertilizer in spring of only 3-4 ounces per established plant for all hydrangea species. The typical N-P-K formulation is 14-3-17, he says.
All plants receive surface/drip irrigation. The garden installs emitter rings around each plant and “links them to create effective zone loops for absolute control of applied water volume and frequency of application,” Condon explains. “It has become our practice to install irrigation within a few days of completing any planting project. Overall, this irrigation approach has had a very positive impact on plant vigor, uniformity of growth, and reduced leaf spotting.”
It all comes down to helping breeders and growers analyze this genus to select the best performer and to perfect new cultivars, Condon says.
In 2020, the test garden named H. macrophylla Summer Crush as the best performer.
“Summer Crush has great pigmentation, and highly pigmented blossoms are en vogue these days,” Condon says.
In 2020, the test garden grew by about 30% and is now almost 3 acres. A group of volunteers nicknamed the Diggermen put in more than 300 hours, including the irrigation work.
“It was surprising what we were able to do and I’m so delighted with the expansion,” Condon says.
Heritage hosted a soft opening — with plenty of safety protocols in place — in August 2020.
There are several ways in which drones can be used to collect inventory data in nurseries and they range from simple to more complex solutions. This article reviews some methods.
Plant count from your monitor or photograph
One of the simplest solutions is to use a low cost drone ($99 to $750) with an RGB/normal camera to generate images of blocks of plants. Once the aircraft is on the ground you simply download the images to a computer. Assuming you captured the entire block of interest, you can print out the image and count the plants using a low-cost ($28) digital counter pen (Fig. 1) in a climate-controlled office. The pen places an ink mark on every plant counted so it is impossible to miscount. If your area of interest cannot be captured in a single image you can use stitching software to merge multiple images. There are several options (e.g., Agisoft Metashape, Microsoft Image Composite Editor, Adobe Photoshop, ImageJ) for stitching images together but we have had good luck with Microsoft Image Composite Editor, which is free. For those with more technical skills, you can develop a method to count plants directly off your monitor. Wouldn’t it be more fun and comfortable to count plants from a climate-controlled office? There are many advantages to this simple method; it is low-cost, immediately adoptable, you can easily store images for later analysis, almost on-demand or near real-time plant counts, and the method is more likely to give accurate plant counts during spring shipping season when production beds look like Swiss cheese and are difficult to ground count. Another advantage to consider is that when all of this work (i.e., drone flight, image collection and processing) is done in-house, you have no concerns about privacy and image data ownership. A downside of this method is that you cannot judge plant quality and grade; you are simply generating plant count.
Plant count using image-based software
This was the area of study that initially perked our interest in drones. The simplistic thought was we could collect aerial images using a drone that we could later analyze using object-based image analysis (OBIA) software (Fig. 2). Some of this software was developed for military applications to rapidly scan satellite images to identify objects of a specific type (e.g., a tank). The process usually involves training the software to look for objects that you are interested in, which in our case, are plants growing in either fields or containers. You typically segment out objects such as the ground cover or weeds to simply focus on the plants of interest. Our research at the University of Arkansas evaluated two commercial software packages (eCognition, Feature Analyst) and a counting algorithm developed by a graduate student at the University of Florida. Our paper in the Southern Nursery Association (SNA) Research Conference in 2015 summarizes our progress up to that point compared to traditional manual methods under nursery conditions (sna.org/resources/Documents/15resprosec03.pdf).
Several companies offer plant counting services (e.g., DroneDeploy/Agremo, PrecisionHawk) for aerial images. Before you go down this route, there are few things to consider. One, make sure the image processing service has the experience counting nursery crops. Many of these services have honed their algorithm for row crops such as corn and soybean. You also want to know how well their software counts plants when the canopies are overlapping which is a common situation in nurseries. Before engaging an outside service, you would also want to be clear ahead of time what kind of specifications they require in images (e.g., minimum number of images, resolution, format) and the limitations of their software. Keep in mind that you may not retain the rights to the information in your aerial images when they are processed by outside companies.
Plant count from RFID tags and a drone
For several years this has been our vision to sweep over beds of nursery-grown plants with RFID tags to quickly and accurately generate plant count (Fig. 3). The delay has always been finding a small RFID reader (interrogator) that could be carried by a small drone. Just in the past two years we finally found readers that were suitable for our application. To work on this approach, we put together a team of researchers in collaboration with industry representatives (e.g., Avery Dennison). The project, which is partially funded by a grant from the Horticulture Research Institute (HRI), was supposed to start at McCorkle’s Nurseries in Dearing, Georgia, in March 2020 but has been postponed until 2021 due to COVID-19. The team has built a prototype system and performed preliminary testing of RFID tag transmission. An overview of our preliminary work was posted by the Southern Region of the International Plant Propagators Society (http://bit.ly/SRIPPS-drones). The general concept of merging sUAS with RFID has already been applied in applications such as indoor warehouses and outdoor car lots. Nurseries provide unique challenges that need to be investigated since there is water, dirt and foliage that can all influence RFID tag signal transmission. Integrating RFID tags will allow traceability of production information to crops from the moment they are tagged until they leave the production facility and beyond. The team also has an interest in collaborating with Arbre Technologies to evaluate gathering their Caliper-RFID data using a drone. A company in California (Senitron: senitron.net/rfid-plant-nurseries-autonomous-drones) advertises that they have already developed a system for nursery producers that merges a drone with RFID tags. The development of an automated plant counting tool for the nursery industry could decrease labor inputs, increase precision and save money.
Acknowledgement: We would like to recognize our collaborative efforts with Drs. Tom Fernandez (Michigan State University), Matt Chappell (University of Georgia) and James Owen (USDA-Wooster).
About the authors: Dr. James Robbins is professor and extension specialist at the University of Arkansas System, Division of Agriculture, email@example.com; Dr. Joe Mari Maja is assistant professor and research sensor engineer at Clemson University’s Agricultural Sciences Department, JMAJA@clemson.edu.