Seed Savers

Conservation

By Katie Mobley

Opposite: Associate Director, Conservation Horticulture and Plant Breeding Peter Zale, Ph.D. assesses the flowers of the globally rare Kentucky lady’s slipper (Cypripedium kentuckiense) for pollination. The plants in this image were started from seeds in 2015 and were among the first to be propagated through our Orchid Conservation Program. Photo by Daniel Traub.

Right: In order to ensure seed development, we often find it necessary to hand-pollinate flowers of some orchids, especially lady’s slipper orchids. This image shows the process of carefully removing the pollinium (concentrated mass of pollen) for transfer to the stigmatic surface to complete the pollination process. In the wild this process would be done by native bees and different types of flies, but many orchids are pollinator-limited. Photo by Daniel Traub.

Opposite: Dr. Peter Zale inspects orchid seedlings growing in test tubes in growth chambers where environmental settings are tailored to the specific conditions native orchids need to grow. Some orchids need only a few months in this environment before planting in the greenhouse, while others can take over a year. Photo by Daniel Traub.

At the heart of plant conservation are core activities essential to the survival of rare species—the simple act of collecting seeds is counted among them. For plants that are globally rare, such as orchids, seed collection often represents the first step of ex situ conservation, where there is concerted effort to identify, collect, and cultivate rare species and determine what it takes to grow them outside of their native habitat. At Longwood, our work to conserve orchids takes place in the fields and forests of Pennsylvania, in far-reaching locations around the globe through our plant exploration, and through specialized research in our laboratory. We are dedicated to this work not only to build upon our own world-class orchid collection, but to advance orchid conservation on a global scale, as we advocate for the conservation of plant resources and collections in our own backyard and worldwide.

Orchids inhabit every continent but Antarctica and make up an extremely impactful 8 to 10 percent of the total diversity of all plants. Yet, despite their global prevalence, all orchids are considered endangered as their populations are generally rare and declining in the wild—an alarming occurrence, as orchids are critically important in determining the overall health of ecosystems worldwide due to their complex ecological interactions with fungi, pollinators, and associated species.

Through our Orchid Conservation Program—which was formalized in 2015 but really dates back to when our founders purchased their first native orchid in 1923— we have used original research to develop innovative and sustainable techniques to grow large seedling populations of native orchids for several reasons: to restore orchid populations native to Pennsylvania, the mid-Atlantic region, and across the country; to continue to build a beautiful, hardy, and genetically diverse orchid collection here at Longwood; and to share techniques for growing orchids in the lab with other gardens and institutions around the world so they may grow and repopulate their own native species.

Among our work in saving and restoring orchid populations native to Pennsylvania is our focus on the fringed or bog orchids of the genus Platanthera Among the most beautiful orchids native to our state, some of these orchids, such as the state endangered Platanthera blephariglottis, are relatively easy to propagate in our laboratory. Others, however, such as the threatened Platanthera peramoena, are among the most difficult native orchids to propagate.

Working with the North Branch Land Trust, an organization that works to conserve the natural, working, and scenic landscapes in northeastern Pennsylvania, we’re currently leading a study in how to most effectively propagate native orchids to both safeguard them and understand how they grow from seed. Using Platanthera as a model, we’re examining how the art and science of horticulture can contribute to conservation, and we’re seeking to answer this basic question: Can they be grown?

To support this study—among many others—Senior Research Specialist Ashley Clayton has established an orchid mycorrhizal fungus bank, containing fungi from several orchid taxa, extracted from the roots of wild adult orchid plants, grown in the laboratory, and maintained in vitro for later use. Here, Clayton uses a microscope to count the number of orchid seeds that have germinated in a Petri dish to compare how sowing the seeds asymbiotically and symbiotically affect orchid seedling development.

To help answer this question, Longwood Laboratory Technician Kevin Allen, who is working on his master’s degree in plant and soil science from Texas Tech University, is conducting the laboratory portion of this study here at Longwood. Through regular visits to northeastern Pennsylvania, Allen has helped collect seeds of these orchids from the field and has sown 257 Platanthera seed capsules into 352 Petri dishes in our laboratory—which equates to hundreds of thousands of dust-like seeds. With the final seeds sown in November 2022, Allen is currently leading the data collection for related germination efforts, observing each dish under a microscope once per month to assess the seeds’ stages of development, and embarking upon statistical analysis through the end of 2023.

Seeds of almost all orchids depend on mycorrhizal fungi to induce their germination in the wild. Mycorrhiza, which means “fungus roots,” is an association between a fungus and a plant’s roots. Allen’s research builds upon our work establishing an orchid mycorrhizal fungus bank. Led by Longwood Senior Research Specialist Ashley Clayton, this bank contains fungi from 10 taxa of orchids (and growing), extracted from the roots of wild adult orchid plants (without harming them), grown in the laboratory, and maintained in vitro for later use.

In some cases, the relationship between a plant and a fungus is mutualistic—or symbiotic—in that the plant and fungus obtain something from one another. In the case of orchids, however, the plants actually parasitize the fungi and use them as a food source both while the seedlings are developing and as adult plants. Through this study, we are working to better understand these relationships and apply them to the cultivation and conservation of native orchids. Part of our exploration is whether or not there is an advantage to germinating Platanthera symbiotically as immature seeds—or those extracted from a green seed capsule before it opens up and browns—compared to mature seeds.

In general, immature seeds are typically easier to germinate as they don’t have the same dormancy factors as mature seeds. Through our Platanthera collection and propagation work, we’re also examining if there’s an advantage to growing these seeds symbiotically, which historically has resulted in a higher germination percentage for mature seeds. Using Clayton’s research, we are examining if growing fungi in a certain way results in successful symbiotic germination, as our ability to grow these fungi will increase our ability to grow the orchid seeds.

Rare native orchids are notoriously difficult to germinate—and symbiotic germination is a very multi-layered process. Perhaps a symbiotic approach, working with immature seeds, may be the way to unlock the secret behind getting them to grow—and conserving them.

Conclusions from this multi-year, multilayered effort remain to be seen. What we do know now is that keeping the orchid’s habitat intact is at the core of conservation efforts. However, if the northeastern Pennsylvania habitat from which we collect these Platanthera seeds were to one day become compromised or inhospitable to these orchids, our growing these native plants outside of their native environment would help ensure they’re here to stay.

Opposite: Conducting the laboratory portion of the Platanthera study, Laboratory Technician Kevin Allen leads the data collection for related germination efforts, which involves hundreds of thousands of dust-like seeds. Here, Allen prepares filters for disinfecting the orchid seeds prior to sowing them in Petri dishes; the seeds are disinfected with a bleach solution and then strained through the paper filters. Photo by Daniel Traub.