Contributed by Alessandra Rella, The McLean Contributionship Education Intern

A couple weeks ago, the interns got to go on a special “insider tour” of Society Hill, where we explored the area through the lens of urban trees. Paul Meyer, the Arboretum’s retired Executive Director, was our guide! We walked through the city parks and streets, making our way from tree to tree. Every few feet we stopped at a tree, examined its appearance and health, and then linked our observations to the surrounding conditions the tree was planted in. Paul taught us a lot about the many different species of trees we saw, the importance of having diversity among trees, and the many factors to keep in mind when planting trees in urban areas. 

Oh, and we also had a special guest join us: Bill Cullina, the Arboretum’s new Executive Director!

We had a really lovely afternoon.

Up next in the intern’s schedule of weekly adventures… tree climbing! Stay tuned for pictures of our lovely interns up in the tops of trees.


Contributed by Anthony Aiello, The Gayle E. Maloney Director of Horticulture and Curator

One of the results of multiple years of plant exploration is the opportunity to find connections in unexpected places. I have been fortunate to work with Michael Dosmann, a colleague at our sister Ivy League institution, the Arnold Arboretum of Harvard University. We have traveled together on expeditions throughout the United States and Asia. In the fall of 2018, our collaboration continued with an expedition to the island of Honshu, Japan, joined by Steve Schneider (Arnold Arboretum), Todd Rounsaville (Polly Hill Arboretum), and Mineaki Aizawa and Tatsuhiko Shibano (Utsunomia University). 

Not only did this two-week expedition allow us to visit six locations where we made 58 collections of 55 different taxa, but more importantly, we gained a deeper understanding of the lessons of biogeography by observing closely-related and similar-looking disjunct species, far from their nearest relatives.  

An extraordinary aspect of this expedition to Japan was observing and collecting species that are closely related to ones that we had seen across China and throughout the U.S.  It was fascinating to get first-hand experience with a trio of species, having previously seen the Japanese counterparts only in cultivation. 

The expedition initially focused on Nikko National Park, located about three hours north of Tokyo, and on our third day in the field, we came across forked viburnum (Viburnum furcatum) growing along the edge of Lake Yuno. With it were massive trees of Japanese arborvitae (Thuja standishii) and hiba false arborvitae (Thujopsis dolobrata), along with thickets of bright-barked Japanese clethra (Clethra barbinervis). Most of the viburnum’s wide, rounded leaves had heavy insect feeding damage, giving it the Japanese common name of mashikari (“always eaten by insects”). Despite this, the growth habit and leaf shape instantly reminded us of two other viburnums seen thousands of miles away: the eastern North American hobblebush (V. lantanoides), and the Chinese counterpart viburnum, V. sympodiale. I had first seen the American species in the Smoky Mountains in 2002 and the Chinese one on a 2005 expedition to Gansu Province.

Throughout this expedition, we made a number of other collections of Japanese species that have familiar North American relatives. There are many examples of the North America-Asia pairings, but fewer examples of the North America-Europe-Asia sets of species. An example of the latter occurrence is beech (Fagus), with the familiar American beech (F. grandifolia) of eastern forests, the majestic cultivated European beech (F. sylvatica), and several less horticulturally known Chinese and Japanese species. While collecting at Lake Yuno, we encountered Japanese beech (F. crenata) growing on a small bluff above the lake.

A few days later, we encountered another impressive beech, Fagus japonica, with a height of some 75 feet, at the University of Tokyo Forestry Department Research Station, in Chichibu (west of Tokyo). In the understory were groves of Japanese pieris (Pieris japonica) and Japanese clethra, and a population of Japanese stewartia (Stewartia pseudocamellia) perched on a steep hillside, elongated and stretching for light among the competing trees. These species are among the most ornamental and desirable of the numerous plants that have come to our gardens from Japan. Seeing them together provided an opportunity to understand their growing requirements, while simultaneously appreciating their beautiful natural arrangements. A choice garden plant, Japanese stewartia is known for its exfoliating bark, large white flowers, and rich autumn leaf colors. 

We collected a second species of stewartia at the last location of the expedition, the Hokkaido University Forestry Station, in Wakayama Prefecture on the Kii Peninsula, the southernmost tip of Honshu. This mountainous region is among the wettest areas in Japan, receiving upwards of 118 inches of annual precipitation. Within this rich, mixed broadleaf-evergreen forest, we made collections from several massive trees of tall stewartia (Stewartia monadelpha), with slick, orange-red bark that grew up to 40 feet tall on steep mountain slopes. The two Japanese species of stewartia highlight another North America–Asia disjunction, reminding us of the mountain stewartia (S. ovata) of the mountainous southeastern U.S., and Virginia stewartia (S. malacodendron), a southeastern coastal representative.

Surrounded by disjunct species–viburnum, beech, stewartia, and maple– we could not help but notice the genera where there is diversity in Asia, but no other temperate counterparts. On one of the days in Wakayama, we also found three species of enkianthus (a genus in the heath family, Ericaceae) related to the more familiar white enkianthus (Enkianthus perulatus). Enkianthus is well-represented by six species in Japan and seven species in China, but with none in North America. It was remarkable to see three distinct species growing together on one mountainside.  Earlier on the trip we collected two other species, bringing our total effort to five of the six Japanese species. 

In contrast to the species diversity of Enkianthus, we made two horticulturally and botanically interesting collections at Wakayama— the wheel tree (Trochodendron aralioides) and Japanese umbrella pine (Sciadopitys verticillata).  Both of these are worthwhile as garden curiosities, but they are taxonomically isolated, so it was fascinating to see these evolutionary “orphans” juxtaposed with those that are species rich with close relatives in both Asia and North America.

If seeing is believing, then this collecting trip to Japan certainly brought me true horticultural religion. The cultural and botanical experiences on these expeditions are priceless; and the ability to see plants growing in their natural environment provides a deeper understanding of their horticultural needs, which we can translate into growing them at the Arboretum.

Contributed by Katherine Wagner-Reiss

Ginkgo translates to “silver apricot,” but an apricot is a true fruit while Ginkgo biloba bears only a fruit-like seed. The seeds are used in Asian cuisine (minus the smelly outer coat), although toxicity has been reported. Photo by Katherine Wagner-Reiss.

Understanding the name Ginkgo biloba will allow you to identify this tree without fail! The genus name is a combination of two Japanese words: gin,”silver,” plus  kyo, “apricot,“ rendered as Ginkgo. This tree, which is native to East China, had long been cultivated in China, Japan, and Korea. When first encountered by a Western naturalist near a temple in Japan, and despite painstaking translation, the “y” in kyo became a “g.” Biloba refers to the characteristic leaves with two lobes. Find either the seeds, which resemble apricot fruits, and/or the fan-shaped bilobed leaves, and you will have correctly identified this tree. Maidenhair-tree is the apt common name, so called because of the similarity of the leaves to the leaflets (pinnae) of the maidenhair fern.

Ginkgo biloba 1932-0021*A. A female specimen from the Morris Estate is easily located near the main parking area. Photo by Katherine Wagner-Reiss.

The Morris Arboretum grows both the straight species Ginkgo biloba and one cultivar Ginkgo biloba ‘Spring Grove.’ ‘Spring Grove’ was found as a witches’ broom mutation on a tree in Spring Grove, Ohio, and has two qualities worth cultivating: it is a male, and it is a dwarf. Male ginkgos are often preferred over female ginkgos whose seeds contain butyric acid, producing a rancid butter smell after they litter the ground in the fall. Male ginkgos have their own downside: abundant pollen in the spring, which can be a respiratory allergen. A dwarf cultivar is a boon to those with a small garden site, since the species can grow to 80 x 40 feet while ‘Spring Grove’ matures at 6 x 4 feet, in 15 years or so.

The bark of a mature Ginkgo biloba is deeply furrowed. Photo by Katherine Wagner-Reiss.

Come to the Morris Arboretum to enjoy Ginkgo biloba, essentially unchanged from when it co-existed with dinosaurs, and also remarkable for an individual life-span that can exceed 1,000 years. The source of two of the Morris Arboretum specimens is the Morris Estate; exact locations can be found mapped on the Collection Connection.  Trace a leaf to see the unusual open dichotomous venation: the leaf veins successively fork into twos and never cross over one another. Wear gloves if you want to handle fallen seeds because they can cause an allergic skin rash. Enjoy the deep gold autumn color of the leaves and then try to witness a phenomenon: unlike most deciduous trees that shed their leaves gradually, the ginkgo leaves fall more or less simultaneously, sometimes in just one day after a hard frost: leaf abscission or magic, believe what you like! 

Gingko biloba ‘Spring Grove’ 2008-070*A . The characteristic bilobed fan-shaped leaves are the source of most ginkgo herbal remedies. Photo by Katherine Wagner-Reiss.

Maidenhair fern leaflets (pinnae) look like miniature versions of ginkgo leaves, leading to the common name of maidenhair-tree for Ginkgo biloba. Photo by Katherine Wagner-Reiss.


Katherine has her Certificate in Botany from the New York Botanical Garden and is a botanical tour guide and freelance writer.

Contributed by Alessandra Rella, The McLean Contributionship Education Intern

Last week we ventured out with Jason Lubar (Associate Director of Urban Forestry) to explore the Wissahickon Valley Park. We eagerly set out on the trail on a humid Tuesday afternoon. Despite the heat, everyone had smiles on their faces as we walked under the sunlit, green canopy and listened to Jason share his knowledge on the surrounding trees, soil, and rock formations. Some attentive interns even noticed a funnel-web spider, tucked away in its perfect tunnel-like home. We took a halfway break at the Spring Mill Covered Bridge and admired the last covered bridge in Philadelphia.

Stay tuned for more news from the interns!