Past Tree Mobs™
Japanese Azaleas: Rhododendron molle ssp. japonicum
Join longtime Arboretum volunteer and rhododendron aficionado George Hibben to learn about the qualities of Japanese azaleas that endear them to hybridizers, with focus on the Arboretum’s Rhododendron molle ssp. japonicum. Meet at Acc. #: 28-98*A. [pdf]
Mutants in Our Midst
Ever wonder how new horticultural forms and varieties come to be? For example, how does a green-leafed shrub morph into a gold-leafed variety, or a white-flowered plant develop from a species with magenta blooms? Join Ned Friedman, Director of the Arnold Arboretum, for the first of three mobs he will lead this spring exploring naturally occurring plant mutations that are the source of most of our horticultural wonders. Meet at Acc. #: 10-68*B, Cercis canadensis, commonly known as redbud. [pdf]
Pyrus pyrifolia, Sand Pear
Senior Research Scientist Peter Del Tredici spoke about one of our older specimens, Pyrus pyrifolia, Acc. #: 7272*C. Native to China, Japan, and Korea, this plant was grown from seed that was collected in Hubei Province, China by E.H. Wilson in 1907. A standout in the Arboretum’s landscape, this plant has provided multi-season beauty on Bussey Hill for more than a century. [pdf]
Lilacs: Syringa oblata and Syringa x hyacinthiflora Hybrids
Lilac season has begun with the earliest of the lilacs coming into full bloom. Plant propagator and lilac expert Jack Alexander introduced us to Syringa oblata and told the story of the creation of the first cultivar of Syringa × hyacinthiflora. Met in the lilac collection on the slope of Bussey Hill at Syringa oblata, Acc. #: 381-2001*A. [pdf]
Dwarf Sweet Box, Sarcococca humilis var. digyna
Sue Pfeiffer, horticultural technologist, explained Sarcococca humilis var. digyna, Accession #: 667-2003*MASS a diminutive, sweet-scented evergreen groundcover, native to China. Sue will also discuss other members of the Buxaceae on display in the Leventritt Shrub and Vine Garden. [pdf]
Prunus mume, Chinese Plum or Japanese Apricot
Along with bamboo and pines, the plant most intimately associated with art, literature, and everyday life in China is Prunus mume, Accession #: 233-2002*B, an early flowering plant in the Rosaceae; with Visitor Education Assistant Maggie Redfern. [pdf]
Jasminum nudiflorum, Winter Jasmine
Brian Leib, manager of the Arboretum’s research greenhouses at the Weld Hill Building, spoke about this species from northern China in the Oleaceae. Grown as a ground-covering shrub or trained as a vine, winter jasmine’s yellow flowers signal the coming of spring. See a specimen in the Leventritt Shrub and Vine Garden at Accession #: 654-2003*A. [pdf]
Chimonanthus praecox, Winter Sweet
Chimonanthus praecox, a member of the Calycanthaceae, is a treasure introduced from Asia before this country was a nation. Michael Dosmann, Curator of Living Collections, spoke about the plant’s history, its virtues, and the challenges it presents to northern gardeners. Find our one and only specimen at the entrance to the Explorers Garden, just off Bussey Hill Road at Accession #: 236-98*A. [pdf]
Hamamelis x intermedia ‘Arnold Promise’
Arnoldia Editor Nancy Rose discussed the traditional uses of witch hazel and the origins and naming of Hamamelis x intermedia. She highlighted the cultivar ‘Arnold Promise’, Accession #: 396-69*A. [pdf]
Timber Bamboo and Others
Bamboo is an evergreen woody plant with many unique features. Biao Jin, a visiting scholar from China, talked about the growth traits, ecology, and Chinese cultural uses of bamboo on Conifer Path at Accession #: 369-80*MASS, Phyllostachys bambusoides. [pdf]
Bornean Trees in Boston
Cam Webb, an Arboretum researcher based in Indonesian Borneo, discussed tree genera that occur both in Southeast Asia and in New England, and what they tell us about the history of tropical rain forests and adaptation to the cold. He highlighted Accession #: 801-87*A, Diospyros virginiana, the common persimmon, south of Meadow Road and opposite Faxon Pond. [pdf]
A California Native Thrives in New England
The bright green foliage of California incense cedar can enliven the dullest winter day. Calocedrus gets its name from the Greek kallos, meaning “beautiful,” and cedrus, originally from Latin meaning “evergreen conifer.” Unlike most other conifers, male cones of incense cedar shed pollen on winter’s winds. Visitor Education Assistant Maggie Redfern presented a pair of trees laden with pollen cones at the base of Peters Hill along South Street, including Accession #: 450-86*G, Calocedrus decurrens. [pdf]
Winter Twigs
Most people who can identify trees have come to recognize them by their characteristic leaves, flowers, or fruit, present during the growing season. But with deciduous trees, one can’t rely on these features during the winter months. Fortunately, each species of tree has a unique signature which can be found by studying its twigs. Arborist Kyle Stephens discussed twigs and the information they hold about their identity and their growth habits, featuring Accession #: 695-80*B, Ailanthus altissima forma erythrocarpa, opposite the cork trees along Meadow Road.
Sleeping Beauty: A Flower Bud Fairy Tale
Deciduous trees appear bare, with no of leaves and flowers during the winter. However, the flowers and leaves that will appear in spring are already present, though hidden. These tiny flowers and leaves begin to grow at the end of summer and remain protected inside the bud in a state of dormancy through the winter. Then the warm kiss of spring wakes them from slumber. Visiting researcher Erica Fadon showed what is happening inside the buds of three different trees in the Bradley Rosaceous Collection, at Accession #: 931-51*A, Prunus sargentii ‘Columnaris’. [pdf]
Fagus sylvatica ‘Tortuosa’
The enigmatic cultivar of the European beech, Fagus sylvatica ‘Tortuosa’, is a rarity in nature. Although now fairly common in cultivation, the tortuous habit of these trees still continues to puzzle botanists. Julien Bachelier shared the many mysteries yet to be solved at Accession #: 2420*A. [pdf]
Mosses: Midgets Among Giants
Curatorial Fellow Stephanie Stuber offered the low down on mosses—some of the plant kingdom’s tiniest members. The presentation met at the summit of Hemlock Hill, near Accession #: 2328-98*A, Tsuga canadensis (Canadian Hemlock). [pdf]
Light in the Larches
Sarah Mathews, Arnold Arboretum Sargent Fellow, discussed how plants sense seasonal changes and the mechanisms that triggers their responses. This mob met in the larches on Peters Hill, near the Mendum Street Gate at Accession #: 10-96*C, Larix gmelinii var. olgensis. [pdf]
Franklinia alatamaha
Senior Research Scientist Peter Del Tredici discussed the Arboretum’s most spectacular accession of Franklinia alatamaha (Accession #: 2428-3*A), from its rich history to a consideration of why this species is extinct in the wild. [pdf]
Katsuras: Hearts of Gold
Curator of Living Collections Michael Dosmann spotlighted the katsura collection as a prelude to autumn. Some of the Arboretum’s oldest accessioned plants (including Accession #: 882*B), katsuras display amazing fall color, and senescing leaves emit the aroma of caramel or burnt brown sugar. [pdf].
Blind Date
Arboretum Director Ned Friedman and Curator of Living Collections Michael Dosmann discussed methods for determining the age of trees, and demonstrated coring techniques with a shagbark hickory on the east edge of Meadow Road. [pdf].
The Mighty Oaks
Guest presenter Dave Barnett, President and CEO of Mount Auburn Cemetery, spoke about the oaks (Quercus spp.) that dominate the landscapes of both the Arnold Arboretum and Mount Auburn Cemetery. The talk took place in the Arboretum’s oak collection, north of Valley Road at the northern end of Oak Path. [pdf].
Ephedra minuta
Stephanie Conway, a visiting fellow in the Friedman Lab at the Arnold Arboretum, spoke in the Leventritt Shrub and Vine Garden about this ancient species, how it is related to conifers, and where—and whether—is should rest on the gymnosperm family tree. [pdf].
Trouble Spot Transformed
Manager of Horticulture Steve Schneider discussed the results of this year’s intern project at the Bussey Hill Seep. Spectators learned how and why this this overgrown and difficult to manage site has been transformed. [pdf].
Magnolia virginiana
This mob met on the slope behind the Hunnewell Building to consider protogynous plant reproduction (i.e. in each flower, the female function precedes the male function) and the seeds that are produced, with visiting researcher Juan Losada. [pdf].
Hanging in There: How Plants Climb – Humulus lupulus ‘Cascade’
The Leventritt Shrub and Vine Garden provided the location for plant morphologist Pam Diggle to talk about the various ways that vines attach themselves to other plants, trellises, walls, and even telephone wires. [pdf].
Goldenrain Tree – Koelreuteria paniculata
Here at the Arboretum, it’s all about the backstory, and every tree has at least one. Curator of Living Collections Michael Dosmann shared a few of the special stories attached to several of our Koelreuteria paniculata (goldenrain tree) accessions. [pdf].
Locust, Legumes, and Nitrogen Fixation
Arnoldia Editor Nancy Rose discussed Robinia pseudoacacia, accession 321-48*A, located near the juncture of Meadow and Bussey Hill Roads. Known commonly as black locust, R. pseudocacia hosts nitrogen-fixing bacteria in its root system, a characteristic shared by many other members of the pea family. [pdf].
Stewartias: Natives, Exotics, and Hybrids
Senior Research Scientist Peter Del Tredici met visitors at the entrance to the Explorers Garden off Bussey Hill Road for a comparison between the many stewartias in the Arboretum collection. Members of the tea family of plants, stewartias are one of six species collected by the Arboretum in collaboration with the USDA and the North American Plant Collections Consortium.[pdf].
Plant Armor: A Thorny Issue
This gathering at the summit of Peters Hill featured Arboretum Director Ned Friedman providing an overview of the evolutionary development of thorns in woody plants. Gleditsia triacanthos, accession 1237-79*C, served as an example of this protective adaptation. [pdf]
Keeping Track of Trees
Visitors to this Tree Mob™ at the summit of Bussey Hill were introduced to the Arboretum’s plant inventory program. Kyle Port, manager of plant records, and Stephanie Stuber, curatorial fellow, explained how and why our living collections are tracked and recorded using Pinus parviflora, accession 1539-71*D, as an object lesson. [pdf]
Pinus densiflora
Participants got to know Pinus densiflora, accession 1724-77*B with Research Scientist Cary Pirone. Cary explained the process of conifer reproduction and described the pollination research she is conducting at the Arboretum. [pdf]
Ginkgo biloba
Senior Research Scientist Peter Del Tredici explained the reproductive biology of Ginkgo biloga at the time of day when the process is visible. Visitors met at Ginkgo biloba ‘Hayanari’, accession 824-83*A, just beyond the Hunnewell Building Visitor Center, and observed the phenomenon with hand lenses. [pdf]
Malus sargentii
Arboretum Apprentice Miles Sax Schwartz introduced visitors to Malus sargentii, accession 20408*D, on Peters Hill. Miles used this plant to illustrate the Arboretum’s long interest in cultivating crabapples, including his recent efforts to reassess and reinvigorate these plants at the Arboretum. [pdf]