The Magazine of the Arnold Arboretum VOLUME 77 • NUMBER 4 The Magazine of the Arnold Arboretum VOLUME 77 • NUMBER 4 • 2020 CONTENTS Arnoldia (ISSN 0004–2633; USPS 866–100) 2 Uncommon Gardens is published quarterly by the Arnold Arboretum Ben Goulet-Scott of Harvard University. Periodicals postage paid at Boston, Massachusetts. 6 Revisiting the Mystery of the Bartram Oak Subscriptions are $20.00 per calendar year Andrew Crowl, Ed Bruno, Andrew L. Hipp, domestic, $25.00 foreign, payable in advance. and Paul Manos Remittances may be made in U.S. dollars, by 12 Collector on a Grand Scale: The Horticultural check drawn on a U.S. bank; by international Visions of Henry Francis du Pont money order; or by Visa, Mastercard, or American Express. Send orders, remittances, requests to Carter Wilkie purchase back issues, change-of-address notices, 24 Eternal Forests: The Veneration of and all other subscription-related communica- Old Trees in Japan tions to Circulation Manager, Arnoldia, Arnold Arboretum, 125 Arborway, Boston, MA 02130- Glenn Moore and Cassandra Atherton 3500. Telephone 617.524.1718; fax 617.524.1418; 32 Each Year in the Forest: Spring e-mail [email protected] Andrew L. Hipp Arnold Arboretum members receive a subscrip- Illustrated by Rachel D. Davis tion to Arnoldia as a membership benefit. To become a member or receive more information, 41 How to See Urban Plants please call Wendy Krauss at 617.384.5766 or Jonathan Damery email [email protected] 44 Spring is the New Fall Postmaster: Send address changes to Kristel Schoonderwoerd Arnoldia Circulation Manager The Arnold Arboretum Front and back cover: Sargent cherry (Prunus sargentii) 125 Arborway was named, in 1908, in honor of Charles Sprague Sargent, Boston, MA 02130–3500 the first director of the Arnold Arboretum. Ten years later, Sargent sent nursery stock of this Japanese orna- Jonathan Damery, Editor mental to Henry F. du Pont, who planted the species at Andy Winther, Designer what is now Winterthur Museum and Gardens. Photo at Editorial Committee the Arnold Arboretum (accession 794-28*B) by Meng Li. Anthony S. Aiello Inside front cover: Pancrace Bessa illustrated the Peter Del Tredici Bartram oak (Quercus × heterophylla) for the second Michael S. Dosmann volume of François André Michaux’s Histoire des Arbres William (Ned) Friedman Forestiers de l’Amérique Septentrionale, published Jon Hetman in 1812. Although Michaux named the taxon Quercus Julie Moir Messervy heterophylla, the label on the illustration is curiously Jonathan Shaw misspelled. Image from Biodiversity Heritage Library. Copyright © 2020. The President and Inside back cover: Bud scales of the shagbark hickory Fellows of Harvard College (Carya ovata) become dramatic centerpieces in spring. Very occasionally, the trees produce a structure that shares characteristics with both a bud scale and a photo- synthetic leaf (bottom, second from right), which shows the relationship between the two leaf forms. Photos and composition by Kristel Schoonderwoerd. Uncommon Gardens Ben Goulet-Scott ith one last gulp of iced tea, I stepped grass to arrive at my modest garden, I wondered out of a rented sedan onto the weedy if I might now be familiar to the eagles of this Wshoulder of Forest Service Road 117 area. I was relieved to find that my plants still to perform my pre-fieldwork ritual. I tucked stood, and in fact, they seemed to be thriving. my pants into my socks, applied sunscreen and The spring before, in 2018, I had worked with bug spray, and pressed a baseball cap over my Robin and lab technician Matt Farnitano to spiky bed head. The morning temperature in plant 321 rooted cuttings at this site, each no western Kentucky was already approaching more than four inches tall. Now many of the 90°F (32°C), unusual for late April. I grabbed plants boasted dozens, even hundreds, of bright my water bottle and tablet from the back seat pink flowers. I set down my water bottle and and turned towards my experimental garden turned on the tablet, ready to record herbivore plot, which was planted with three subspecies damage and count flowers for as long as the of pink-flowered herbaceous Phlox. As a doc- daylight permitted. toral student working with Robin Hopkins, a This plot is a type of experiment known as a faculty member at the Arnold Arboretum, I common garden. Three different taxa—Phlox have returned regularly to western Kentucky pilosa subsp. pilosa, P. pilosa subsp. deamii, and Tennessee to study the role of local adapta- and P. amoena—had been planted in a random tion in the divergence and speciation of these order, and because the growing conditions are closely related lineages. consistent, any differences in traits among the A skeletal dead tree stood on the opposite three taxa can be ascribed to genetic differences side of the field, a favorite perch for large birds. rather than plastic responses to the environ- I recognized the familiar broad-shouldered sil- ment. Common garden experiments have a rich houette and gleaming white head of an adult history in plant biology. Botanists in the first bald eagle. Surely it had long since noticed me half of the twentieth century (especially Göte and my car, and as I pushed through the tall Turesson, Jens Clausen, David D. Keck, and GOULET-SCOTT, B. 2020. UNCOMMON GARDENS. ARNOLDIA, 77(4): 2–5 Phlox Common Garden 3 William Hiesey) made foundational contribu- entirely obvious to my human senses, I let the tions to our current understanding of heritable wild populations guide me to appropriate sites variation in natural populations using common for the experiment. gardens. Outside the Weld Hill Research Build- Settling into my morning work routine, I ing at the Arnold Arboretum, other researchers opened a spreadsheet on my tablet that con- are using a series of common garden plots to tained a stack of three-digit codes in a column study the ecology, morphology, and physiology on the left. Each code corresponded to a unique of woody plants. In fact, the entire Arnold Arbo- plant identifier that was stamped into an alu- retum can be viewed as a large common garden, minum tag and fastened in the ground at the with plant species and varieties from around base of each plant. In order to test for local adap- the world growing in one location. tation, I designed my experiment to evaluate My research in Kentucky required not one traits related to fitness, like susceptibility to but three common gardens, one in each habitat herbivore damage and total reproductive out- of my three study taxa. During the summer of put. My goal on this visit was to score the pres- 2017, I had traveled throughout the native ranges ence or absence of herbivore damage and count of these three subspecies in the southeastern the number of open flowers on every plant. I United States and collected plant material for labeled two new columns (“herbivory_2” and the gardens. Perennial Phlox propagate well “flowers_2”) and eased into a cross-legged seat from cuttings, so I collected single stems from on the edge of my plot. wild plants, leaving the rest of the plant in the Collecting these data was a comprehensive ground. I mailed these stems back to labmates sensory experience. As I pushed and pulled at the Weld Hill Research Building who planted inflorescences aside to reveal more clusters of them in soil so they would produce roots. After bright pink, my fingers reluctantly harvested one year in the Weld Hill greenhouses, they fur- the sticky secretion that protects the flowering nished three cuttings each, allowing me to plant branches of Phlox pilosa subsp. pilosa. Each a genetically identical panel of cuttings in each time I agitated a bunch of flowers, a small flare garden. All three of my common gardens sit of sweet fragrance mixed with the sharp scent adjacent to a wild population of one of the three of spring grasses and forbs soaking in the mid- subspecies. This experimental design—plant morning sun. The exaggerated buzz of a car- all taxa in all habitats—is called a reciprocal penter bee hummed under the exclamations of transplant. I repeated any measurements taken chattering songbirds. A jumping spider tickled in this garden in the other two, both within a across my wrist. Sitting quietly, eye-level with couple hours’ drive. the asters (Erigeron philadelphicus), I immersed A reciprocal transplant is a powerful test for myself in the dense fabric of interactions that local adaptation. Populations that are adapted contributed to the deceptively neat figures in to different ecological niches are unlikely to my spreadsheet. encounter each other in their distinct habitats, This common garden, in the full-sun habitat and if they do, the nonlocal taxon is likely mal- of Phlox pilosa subsp. pilosa, is tucked into the adapted and will not persist. Local adaptation, northern tip of a 170,000-acre inland peninsula therefore, may contribute to the divergence (the largest in the United States), which spans of closely related lineages. In general, Phlox the border between Kentucky and Tennessee. pilosa subsp. pilosa favors open grassy areas in When the Tennessee Valley Authority com- full sun, while P. amoena grows in the grassy pleted the two dams that isolated this strip of fringes of mixed hardwood forest, and P. pilosa land, aptly named Land Between the Lakes, the subsp. deamii peppers the understory of similar residents were forced to move, leaving their forest edges. But because the ecological factors properties to be reclaimed by mixed hardwood that differentiate the preferred habitats of my forest. The house that complemented this yard three Phlox taxa are multidimensional and not and surrounding fields has long since been Facing page: Intermixed Phlox subspecies flower in the author’s common garden in the Land Between the Lakes region of western Kentucky.