The Magazine of the Arnold Arboretum VOLUME 74 • NUMBER 1 The Magazine of the Arnold Arboretum VOLUME 74 • NUMBER 1 • 2016 CONTENTS Arnoldia (ISSN 0004–2633; USPS 866–100) 2 A Concise Chronicle of Propagation is published quarterly by the Arnold Arboretum Tiffany Enzenbacher and of Harvard University. Periodicals postage paid John H. Alexander III at Boston, Massachusetts. Subscriptions are $20.00 per calendar year 14 Unlocking Ancient Environmental Change domestic, $25.00 foreign, payable in advance. with the Help of Living Trees Remittances may be made in U.S. dollars, by John M. Marston check drawn on a U.S. bank; by international money order; or by Visa, Mastercard, or American 23 Cork: Structure, Properties, Applications Express. Send orders, remittances, requests to purchase back issues, change-of-address notices, Lorna J. Gibson and all other subscription-related communica- tions to Circulation Manager, Arnoldia, Arnold 28 Ulmus thomasii: The Hard Elm That’s Arboretum, 125 Arborway, Boston, MA 02130- Hard to Find 3500. Telephone 617.524.1718; fax 617.524.1418; Brian Pruka e-mail [email protected] Arnold Arboretum members receive a subscrip- Front cover: In this issue, Manager of Plant Produc- tion to Arnoldia as a membership benefit. To tion Tiffany Enzenbacher and Plant Propagator John H. become a member or receive more information, Alexander III describe the process of moving seeds and please call Wendy Krauss at 617.384.5766 or other propagules through the Arboretum’s plant produc- email [email protected] tion system. Seen here, a linden viburnum accession (Viburnum dilatatum, 1804-77) grown from seeds col- Postmaster: Send address changes to lected during an Arboretum expedition to the Republic Arnoldia Circulation Manager of Korea in 1977. Photo by Nancy Rose. The Arnold Arboretum 125 Arborway Inside front cover: View of a section of the Dana Green- Boston, MA 02130–3500 houses in 1978. Archives of the Arnold Arboretum. Nancy Rose, Editor Inside back cover: The Arboretum’s lone specimen of Andy Winther, Designer rock elm (Ulmus thomasii, 444-88-A) grows on the east- Editorial Committee ern slope of Bussey Hill. Photo by Brian Pruka. Anthony S. Aiello Peter Del Tredici Back cover: This specimen of Henry maple (Acer henryi, Michael S. Dosmann 164-83-A), a Chinese species that bears drooping clus- William (Ned) Friedman ters of winged fruits (samaras), was grown from seeds Jon Hetman received from the Hangzhou Botanic Garden in China. Julie Moir Messervy Photo by Nancy Rose. Copyright © 2016. The President and Fellows of Harvard College CAMPAIGN FOR THE A Concise Chronicle LIVING COLLECTIONS of Propagation The Campaign for the Liv- Tiffany Enzenbacher and ing Collections kicked off last fall with plant col- John H. Alexander III lecting trips to China and Idaho, which Curator of lant propagation historically has been recognized as an Living Collections Michael integral component of the Arnold Arboretum’s mis- sion. In fact, the Arboretum’s second employee (inau- Dosmann and Manager of P gural director Charles S. Sargent was the first) was plant Plant Records Kyle Port propagator Jackson Dawson, hired in 1873, the year after wrote about in the last issue the Arboretum was established. Since Dawson was Sar- of Arnoldia. Once newly gent’s only employee, he served not only as the propagator acquired fruits, seeds, cut- but also the superintendent (Geary and Hutchinson 1980) and remained with the Arboretum until his death in 1916. tings, divisions, and plants The Arboretum’s other long-term and influential propaga- arrive at the Arboretum, the tors—William H. Judd (employed from 1913 to 1946), Alfred production staff at the Dana J. Fordham (1929 to 1977), and John H. Alexander III (1976 Greenhouses takes over. In to 2016)—and shorter-term propagators followed suit after Dawson. Through horticultural expertise, experience, and this issue, Manager of Plant old-fashioned trial and error, they coaxed seeds to germinate Production Tiffany Enzen- and cuttings to grow roots, successfully propagating taxa bacher and Plant Propaga- novel to New England and North America. The propagation tor John H. Alexander III facilities have moved five times over almost a century and a half and have seen many exciting horticultural accomplish- describe the process of shep- ments by Arboretum propagators and production staff. herding new accessions from In 1873, the Arboretum shared growing space with the the greenhouse bench to final Bussey Institution, then relocated in 1886 to a small land production nurseries, the last plot and 20-foot by 50-foot greenhouse on the property at 1090 Centre Street, where Dawson then resided (Geary and step before plants move to a Hutchinson 1980). These modest accommodations were permanent location on the soon outgrown and a new greenhouse was constructed on Arboretum grounds. Orchard Street across from the Arboretum (off of the Arbor- way) in 1917 (Howard 1962). With intensified Arborway traffic and road widening, production was moved back to land adjacent to the Bussey Institution in 1928. As addi- tional space needs arose, along with the desire for a more up-to-date building, ground broke to construct the Charles Stratton Dana Greenhouses in 1961. The donation for the Greenhouses was provided by Mrs. William R. Mercer (née Martha Dana), and was named in honor of her father, Charles S. Dana (Howard 1962). This complex houses the present facilities, including specialized equipment and envi- ronments for seed, cutting, and grafting propagation, green- house and outdoor bench space for containers, an evaluation Propagation 3 ARCHIVES OF THE ARNOLD ARBORETUM The Arnold Arboretum’s greenhouse at the Bussey Institution was built in 1928. This view is of the greenhouse interior in 1949, photographed by Heman Howard. TIFFANY ENZENBACHER TIFFANY ARCHIVES OF THE ARNOLD ARBORETUM Recent renovations to the Dana Greenhouses increase efficiency and save water and energy. The seed propaga- tion house is now equipped with an improved mist sys- tem that features hanging mist assemblies, which allows for maximum use of bench space. Other revamped features include sectioning the house into three irriga- tion zones with as many isolation valves in each zone, which allows for the flexibility to tailor water needs to specific taxa. Mist frequency can be controlled to come on at intervals of 2 to 180 minutes, with the duration of a mist event ranging from 2 to 60 seconds. LED (light- emitting diode) lighting was installed in fall 2015. The LumiGrow Pro 325 LEDs utilize 70% less energy than our previous HID (high intensity discharge) lamps and Views of the Dana Greenhouses in spring 1966 by Heman How- produce 70% less heat. Lights are used to extend the day ard (above) and again in fall 1974 by Alfred J. Fordham (below). length during short days. 4 Arnoldia 74/1 • August 2016 KYLE PORT nursery, three longer-term nurseries, a cold storage building for overwintering containers, and the Bonsai and Penjing Pavilion. Through facility relocations and many staff changes in the years since the Arboretum’s inception, plant propagation and production have remained center stage. The current ten- year Campaign for the Living Collections (Fried- man et al. 2016), which focuses on acquiring nearly 400 wild-collected plant taxa, will assur- edly keep propagation in the limelight well into the future. The Campaign’s list of desiderata features taxa selected because they increase the phylogenetic and biological breadth of Arbore- tum collections, belong to geographically dis- junct clades, are marginally hardy or threatened in the wild, or can be used to create a “living type specimen” in genomic research. Last September, the Dana Greenhouses staff received 100 new accessions (seeds, cuttings, plants) from expeditions related to the Cam- paign. Seeds from many accessions have already germinated, and others such as paperbark maple Fleshy fruits like these from wild-collected Washington (Acer griseum) may take several cycles of warm hawthorn (Crataegus phaenopyrum) are soaked, rubbed, and cold stratification to germinate uniformly. and sieved to separate the pulp from the seeds. We look forward to transitioning individuals (APHIS) requires a specialized permit to import through the phases of production here at the foreign seeds into the United States. This per- Dana Greenhouses, with the end goal of having mit allows for the importation of a small quan- plants in their permanent locations in the living tity of seeds, pending a successful evaluation for collections for researchers to study, children to hitchhikers—noxious weed or parasitic plant learn from, and the public to enjoy. seeds, insect pests, or pathogens of concern. The Arboretum typically has seeds routed to PROPAGATION MATERIAL ARRIVES the APHIS Plant Protection and Quarantine In autumn, as plants in the living collections inspection station at John F. Kennedy Interna- are slowing in growth and their foliage begins tional Airport in Jamaica, New York. Because to abscise, the “growing season” in the Dana the several day to weeklong inspection process Greenhouses is just commencing. Production is so complex and vital, foreign seeds have to staff is overwhelmed with anticipation about be clean (removal of fruit surrounding seeds), what seeds, fruit, cuttings, and plants we will properly labeled, and limited to only 50 seeds be receiving from foreign and domestic expedi- (or 10 grams [0.35 ounces]) per package. Should tions. However, once the highly sought-after the scrutinizing