Walking along a trail in an evergreen forest in the foothills of the Himalayas in north central Myanmar in 2002, Botany Curator John Kress came across a plant that appeared to be a species of Hitchenia (Zingiberaceae). The plant had no flowers, so he collected a living specimen and brought it back to Washington, DC, for further study. Placed in the hands of the Botany Research Greenhouse manager, Mike Bordelon, it took two years and plenty of care for the plant to flower. During a hot summer day, while hand-watering and soil-checking, Bordelon found at the base of the plant an inflorescence with open flowers. While examining the flowers, Kress decided that this was not Hitchenia, but something new to science instead. What was collected from Myanmar and growing in the greenhouse was a new genus, Larsenianthus. The genus was named after Kai Larsen, a Danish botanist and expert on the flora of Thailand and Zingiberaceae. The species was named L. wardianus, in honor of the famous British plant collector Francis Kingdon-Ward who explored Upper Burma in the first half of the 20th century.
It is not uncommon for plants to be collected in the field and brought back to the Research Greenhouses to watch them grow. What is uncommon is for a new genus or a new species to be discovered after the collected plant flowers. Currently growing in the greenhouses, for example, are an additional eight different flowering plants of Curcuma (Zingiberaceae) from Southeast Asia that may turn out to be species new to science after further research is completed. Additional Curcuma plants in the greenhouse collection have yet to flower—are they known species or are they new species awaiting description?
Gingers and other monsoonal plants that go through a winter dormancy period can be challenge to the greenhouse staff. Some of these plants have a much longer growing season in Asia than what the mid-Atlantic can offer. These longer-season species flower at the end of the growing season, but DC summers are not always long enough for these plants. By cranking up the greenhouse heat in February, the greenhouse staff is attempting to jumpstart the growing season, thus encouraging the plants to come out of dormancy earlier. Time will tell if this approach will help encourage these nameless plants to flower.
Constructed in 1994, the greenhouse consist of five separate houses totaling 6,000 square feet under glass, and another 4,000 square feet of outdoor, above ground growing space. The tallest house reaches a height of 28 feet and contains a 25-foot Ravenala madagascariensis (Strelitziaceae). The four other houses peak at 15 feet, and each maintains a different set of growing conditions—different seasonal temperatures and different humidity levels.
The living collections come from six continents, with a majority from the tropics, and originate from both wild and cultivated sources. The collections represent the research interests of the curators who have the most active greenhouse research programs: Robert Faden’s Commelinaceae, John Kress’ Zingiberales, Jun Wen’s Vitaceae, and Ken Wurdack’s Euphorbiaceae. Other curators with plant material in the greenhouses include Pedro Acevedo’s Sapindaceae, Paul Peterson’s Poaceae, Warren Wagner’s Onagraceae, and Emeritus Research Botanist Laurance Skog’s Gesneriaceae. Most impressive are the collections of Commelinaceae and Zingiberales, ranked as the largest living collection under glass in the world of those two families. Collections have been derived from field collections of department staff and donations from individuals and institutions from around the world. Rarely plants can be grown from seeds found on herbarium specimens or from fleshy bases of “dried” specimens that had resisted total desiccation.
In its mission, the Botany Research Greenhouses maintain a living collection which serves six primary purposes: (1) identification, (2) preserved specimens (vouchers), (3) chemical and genetic analyses, (4) documentation of biological processes, (5) scientific illustration, and (6) photography.
One purpose of the living collection is the documentation, identification, and description of a species. As exemplified in the Larsenianthus story, precise identification in the field may be difficult for a plant not in flower. Thus material is collected and grown in the greenhouses until it flowers and can be identified. Such is the case of another ginger, Curcuma arracanensis, from the cloud forests of Myanmar, a species that Kress and recently graduated Ph.D. student Vinita Gowda described and named earlier this year. A plant may also be identified and vouchered in the field, but after it flowers again in the greenhouse, a second voucher is necessary to verify the original identification. On occasion a curator will be asked to verify an identification of a species, and thus they will request to see the plant in person, asking for cuttings, seeds or the whole plant. These plants are maintained in the greenhouse as well.
A second purpose of the greenhouse is the preservation of specimens. When wild plants are pressed in the field, material such as flowers or seeds may be missed during the original collection. Growing a plant in the greenhouses allows the collector to make a more complete voucher. Plants obtained from other institutions are almost never in flower, so they must be grown until they do flower and a voucher specimen can be prepared.
A third purpose is that living plants in the greenhouse are a more convenient source for chemical and molecular analyses. Proteins, which may be used in population studies, are easier to extract from living material than dried specimens. Proteins from fresh material are not degraded compared to preserved plants. In addition, the living collections provide the best and most convenient tissue for genomic investigations. It is important to maintain plants over a long period of time because new techniques, e.g. phylogenetic studies using DNA (or RNA) and new techniques for studying chromosomes, often require living plants. Studies of comparative plant anatomy of different species and genera of Commelinaceae, for example, have often served as research projects for interns.
A fourth purpose is that different stages of a plant’s life history can be documented. While making collections in the field, only one life stage of a plant will be seen on the day that it is collected—typically, either the vegetative or reproductive stage. In the greenhouse, each stage, from seedling, to flowering, to fruiting can be documented. In addition, the type of flowers a plant produces may change over the course of a single day, and those changes can be recorded as well. In recording floral phenology, the exact time of day the flowers open and fade, the position within an inflorescence, and the sequence of opening and closing of different flower types, such as male and bisexual or female flowers, can be studied with living plants.
Scientific illustration of a plant species serves an additional purpose for maintaining a living collection. Often, plant illustrators like the Botany Department’s Alice Tangerini will use herbarium species to ascertain morphological detail while drawing. Photographs can provide an additional source for the illustrator. But a living plant can allow for an easier and more complete illustration than a pressed specimen or a photograph, and in the case of plants whose flowers are ephemeral, such as all Commelinaceae, living plants are by far the best material for illustration.
Finally, in addition to illustrations, documenting a plant in flower can be captured with photography in the greenhouse. Photographs can catch the shape and color of a plant lost in a herbarium specimen. The Greenhouse Highlight webpage draws attention to some of the interesting plants among the collections housed in the departmental greenhouses.
An additional purpose of the collections, not explicitly spelled out in its mission, is the value for ex situ conservation. The plants in the greenhouse are collected for research and identification, and not specifically for conservation. However, after the plants are accessioned by the greenhouse, and their conservation status is assessed, every effort is made to maintain the plants of threatened species.
Plant Search webpage. Plant Search allows users to locate rare and threatened plant species in cultivation around the world for research purposes, using a database of living collections submitted to BGCI by the world’s botanic gardens. According to the database, one-fourth of the known species in the research greenhouse collections (178 of 707 species) occur in no other botanic garden or greenhouse collection. This number will surely climb as more unspecified taxa in the collection are identified. Fourteen species in the greenhouse collections are listed as threatened (i.e., Critically Endangered, Endangered, or Vulnerable) in the IUCN Red List. Many more species in the collection may in fact be threatened, especially those collected from Africa and Asia, but the conservation status of these species have yet to be assessed by IUCN. The role of maintaining threatened species in the greenhouse is important, given that the goal of Target 8 of the Global Strategy for Plant Conservation is to have “at least 75 percent of all threatened plant species in ex situ collections.”
The research greenhouse would not function so smoothly if not for the care and dedication of the greenhouse staff. Mike Bordelon has been the Greenhouse Collections Manager for the past 18 years. Bordelon, a University of Maryland graduate (B.S. in Botany), was the greenhouse production manager for 15 years at Behnke Nurseries in Beltsville, Maryland, before Kress sought him out to manage the research greenhouses in 1994.
Leslie Brothers, the Assistant Manager, cares for the plants, manages the specimen data and serves as the greenhouse photographer. Also a graduate of the University of Maryland (B.S. in Zoology), Brothers first joined the National Museum of Natural History in 1985 as inventory specialist and then data management for the Department of Entomology, and then joined the Department of Botany in 1989 as Skog’s research assistant. Brothers transitioned from the herbarium to the greenhouse in 1995.
The original Botany Research Greenhouse was built in 1977, in the east courtyard of the National Museum of Natural History. Deborah Bell was the original Greenhouse Collections Manager followed by Susan Richardson, and Curator Robert Read was instrumental in its design. It was located on top of the Osteology Preparation Laboratory, a place where a colony of dermestid beetles would consume all soft tissue on animal skeletons for museum research and display. The overwhelming odors from lab were something to be endured by the greenhouse staff and researchers.
The original greenhouse consisted of one room and 1,000 square feet and was reached by climbing up a two-story metal staircase outside of the building. Supplies and materials were clumsily delivered using a chain-operated outdoor lift. From September until March, the greenhouse had no direct sunlight, blocked by the main building and the museum’s east wing, and thus supplemental light was a necessity. The greenhouse was populated with Read’s bromeliads, Skog’s gesneriads, Thomas Soderstrom’s herbaceous bamboos, Edward Ayensu’s dioscoreas, and plants that were needed for the museum’s Insect Zoo exhibits. When Faden joined the Botany Department in 1980 he brought with him a large collection of living Commelinaceae. A few plants in the original collection still exist today, including Aneilema beniniense that Faden collected in 1969 in Kenya and Palisota hirsuta that Faden collected in 1974 in Ghana. In 1994 the Botany Department moved the greenhouse collection to the larger, more modern facility at MSC, and the museum filled the east courtyard with offices and collection space.
The current challenges that face Bordelon and Brothers are not too different from what most greenhouse staff encounter: controlling insect pests and maintaining complex machinery. The greenhouse practices Integrated Pest Management (IPM), using predatory insects such as the mealy bug destroyer (Cryptolaemus montrouzieri), Rhyzobius beetles, and parasitic wasps to control for mealy bugs, scales, aphids, thrips, and whiteflies. Soft insecticides are also employed, which have short re-entry intervals and tend to be less harmful – though not harmless – to the beneficial insects that are used. Pathogens prove difficult to control, especially in the gesneriad collection, which is susceptible to impatiens necrotic spot virus (INSV). The biggest day-to-day challenge is the need to maintain effective machinery, such as transformers, vents, fans, control boards, fog systems, and lights. Earlier this year, the greenhouses were hit during a lightning storm, which blew out almost all of the transformers. Two years ago, a significant snow storm collapsed the roof of the shade house. Fortunately, the 2011 earthquake did not lead to any structural damage.
The greenhouse is not open to public, although it is often included on SI Resident Associate tours of the MSC complex. It is used by researchers and visiting scientists that have a direct need to use the greenhouse. Access to the facilities is allowed with prior arrangement or notification of the greenhouse staff, which aids in the timing of pesticide applications and other needs.