Contributed by Katherine Wagner-Reiss

Platanus × acerifolia (London planetree) Leaf sinuses/indentations intermediate in depth between the parent trees. Spherical fruit heads, two on a stalk, intermediate in number between the parent trees. Photo by Katherine Wagner-Reiss.

Platanus × acerifolia (London planetree) 1948-8600*A This tree is  described as one of the 17 major trees of the garden. Photo by the Morris Arboretum.

The romance began in 17th century Europe when west first met east. Platanus occidentalis (“western”, range is E. North America) was planted near Platanus  orientalis ( “eastern” , range is W. Asia  and SE. Europe). Some hold that this serendipitous tryst occurred in Spain and others that it occurred in London. With help from the wind, they became parents to the hybrid Platanus × acerifolia (with leaves like maple).  Platanus (“broad,” referring to the leaf) was the ancient Greek name for P. orientalis. 

Here are the common names: American planetree or sycamore for Platanus occidentalis, Oriental planetree for Platanus orientalis, and London planetree for Platanus ×  acerifolia

Platanus × acerifolia is an excellent example of  “hybrid vigor,” the phenomenon of  some hybrid progeny to grow more vigorously than either parent. P. ×  acerifolia  shows some traits that are intermediate between those of each parent, such as pattern of bark exfoliation, depth of leaf lobation and number of fruit heads per stalk; what is not intermediate is the ability of P. × acerifolia to endure the stress of  urban living: the hybrid surpasses each of its parents in that regard.  It tolerates soil compaction near sidewalks, pollarding to restrict its size, and air pollution.  Exfoliating bark is postulated to promote shedding of both city pollutants and living pathogens. While called “London” planetree because London was the first city where it was extensively planted, it is now widely planted in temperate cities including Sydney, Los Angeles, New York, and Rome.

The Morris Arboretum grows twenty-nine Platanus occidentalis, (two are var. glabrata); the variant name, glabrata, means “made nearly free from hair,” referring to the leaves. Researching the variant name led to this interesting finding: the underside of the usual young sycamore leaf has many trichromes (so-called hairs) that blow off in the wind and irritate human eyes and throats; since var. glabrata has fewer trichromes, humans should benefit, although the young leaves might miss the protection that trichromes provide against excessive water evaporation and insect herbivory!

Platanus occidentalis 2002-362*C Insert shows shallow sinuses/indentations creating the lobed leaf. Notice spherical fruit heads, one on each stalk. P. orientalis produces three to six per stalk, and Platanus × acerifolia is intermediate with one to three per stalk. Photo by Katherine Wagner-Reiss.

Platanus orientalis 1964-217*A  Insert shoes deep sinuses/indentations creating the lobed leaf. P. orientalis has the deepest sinuses, P. occidentalis has the shallowest sinuses, and Platatnus x acerifolia is intermediate. Photo by Katherine Wagner-Reiss.

The Arboretum has three Platanus orientalis. The one pictured here arrived in 1961 as seed from the botanical gardens at the University din Cluj- Napoca in Romania and was accessioned in 1964. The second was received in 1996 as a cutting from G. Morgan, M.D. and the third came in 2017 as a seedling from the Arnold Arboretum in Boston.

 The Arboretum has two Platanus × acerifolia plus three cultivars of Platanus x acerifolia: ‘Bloodgood,’ ‘Liberty,’ and ‘Columbia.’    ‘Bloodgood’ was an early selection for resistance to anthracnose, a fungal pathogen. Keeping in mind that P.orientalis is resistant to anthracnose  and that P. occidentalis is susceptible to anthacnose, the National Arboretum performed a new intentional cross between a Turkish P. orientalis  and an American P. occidentalis  to produce  ‘Liberty’ and ‘Columbia,’  anthracnose-resistant cultivars.

While P. occidentalis (sycamore) is native to Pennsylvania and can be seen growing wild alongside streams, and P. × acerifolia (London planetree) is a commonly planted tree in the city of Philadelphia, seeing P. orientalis (Oriental planetree) in cultivation is a rare treat.  Come to the Morris Arboretum to see parents and progeny in one garden.  Locations can be found at Collection Connection.

 Compare, contrast, enjoy.

And, Happy Valentine’s Day!


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

Contributed by Tony Geiger

American Kestrel

I have been to many birding spots in Philadelphia, but the Arboretum is fast becoming a new favorite spot of mine. Thanks to the many different habitats and plants that attract wildlife, the Arboretum always has great birding potential, even in winter. I recently had the pleasure of participating in two bird counts that Morris Arboretum has participated in for the past several years. 

On December 14th, Bob Gutowski, Peter Burns, and myself met at Morris Arboretum on a wet and unseasonably warm morning for the Audubon Christmas Bird Count. The nation-wide Christmas Bird Count is the oldest ongoing citizen science project in the country, dating back a staggering 120 years. For me, the fun part of the Christmas Bird Count, or any bird count, is the perspective we gain from actually putting a number to all the birds around us. In four hours, we found 36 species and roughly 1600 individual birds. This was all within the borders of the Arboretum and Bloomfield Farm (with the exception of some flyover Tundra Swans). Of note were birds such as Common Yellowthroat, which thrive in the Arboretum’s wetlands, and American Kestrel, a type of small falcon which relies on meadows and farm fields for hunting grounds. 

Ruby-crowned Kinglet

Next up was the annual Philadelphia Mid-winter Bird Census, a count organized by the Delaware Valley Ornithological Club for the past 33 years. Bob Gutowski, Jim Best, and myself met at the Arboretum on January 12th for another unseasonably warm day of birding. Buzz, the arboretum cat, even hiked along with us for part of the count, and was surprisingly helpful. We identified 33 species and over 700 individuals within the confines of the Arboretum (note - this count does not include the Bloomfield Farm side, as this falls outside of Philadelphia County limits). Of note were a flyover Bald Eagle, Winter Wrens, and a Swamp Sparrow - all of which are attracted to the Arboretum’s Wetlands and Streams. We also observed tiny and colorful Ruby Crowned Kinglets and Golden-Crowned Kinglets, which spend the winter feeding on seeds in the various conifers around the Arboretum.

Thanks to volunteer counters and resources like eBird, we know that an amazing 168 different species of birds have been seen at the Arboretum, and that number could easily grow. If you’re interested in birding at the Arboretum, check out our online resources, including a list of birds that can be seen through the different seasons. And please join us for some of our upcoming programs. Happy Birding!


Contributed by Katherine Wagner-Reiss

Cryptomeria japonica ‘Yoshino’ 93-223-A Located at the back right corner of the Rose Garden. ‘Yoshino’ is valued for rapid growth and a pyramidal growth habit. Insert shows the flaky red bark responsible for the common name of Japanese-cedar. All photos by Katherine Wagner-Reiss.

Cryptomeria japonica ‘Yoshino’ 93-223-A Note the tooth-like projections on the scales of this mature female cone.

Cryptomeria: the name translates from the Greek as “to hide a part.”  But what “part” is hidden? D. Don, credited with naming the genus Cryptomeria in 1838, described pollen-producing structures “concealed” inside the bases of the male cone scales— the hidden parts! To date, Cryptomeria is a monotypic genus i.e. it has only one species, Cryptomeria japonica.  Japonica means “of Japan,” although, in addition, the range of Cryptomeria includes China.

The common name is Japanese-cedar. Notice the hyphen. In common names the hyphen denotes “so-called.” In other words, this is not a cedar. True cedar (Cedrus) is in the pine family, while Japanese-cedar is in the cypress family. The common name is an understandable misnomer, however, because the bark of Cryptomeria is reminiscent of cedar bark: red, flaky, and scented.

Cryptomeria japonica ‘Yoshino’ 93-223-A Numerous immature male cones will mature and release allergenic pollen in the spring. Hidden pollen-producing parts within these cones are the inspiration for the name Cryptomeria, which means “to hide a part.”

Cryptomeria is the national tree of Japan, a well-deserved honor considering its evergreen foliage, impressive height (up to 230 feet) and shapely conical habit; superficially, it resembles the giant sequoias of California, also in the cypress family. Sugi, the common name for Cryptomeria in Japan, is cultivated on plantations there for use as timber; the abundance of pollen-producing cones causes problematic hay fever-like allergies in the spring, so that cultivars with fewer male cones are being developed.

Morris Arboretum grows the straight species Cryptomeria japonica plus nine different cultivars each with a special feature, often highlighted by the name: ‘Black Dragon,’ ‘Elegans Nana,’ ‘Globosa,’ ‘Globosa Nana,’ ‘Jindai-sugi,’ ‘Lobbii,’ ‘Spiralis,’ ‘Tansu,’ and ‘Yoshino.’  Nana means “dwarf;” the dwarf species are especially desirable for rock gardens and bonsai.

More than 40 cultivars of Cryptomeria with varied heights, habits, and foliage colors are waiting to be enjoyed at arboreta and landscape stores. Don’t be afraid to touch them; an added bonus is soft foliage! Whether you want to check them out before purchasing one for your own garden or just want to enjoy a winter walk, the exact locations of all of the Cryptomeria at the Morris Arboretum can be found in the Collection Connection.

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

Contributed by Pamela Olshefski, Curatorial Assistant

Although a few hollies (Ilex) remain from the Morrises’ time, most of the collection was planted on the four acres of land the Arboretum acquired with Gates Hall in 1948. This slope was selected from its southern exposure and well-drained soils. Henry Skinner, the curator at the time, planted the hollies in the early 1950s with American hollies (I. opaca) at the top of the slope, and more tender species such as English and Altaclera holly (I. aquifolium and I. × altaclerensis) in the shaded lower areas. As a result of this significant collection, we are recognized as an official Holly Society of America arboretum.

Currently, we have about 177 types of evergreen holly—one of the largest collections in the Delaware Valley, with many plants remaining from 50 years ago. For the past several years, we have been renovating the holly collection by removing unknown or unhealthy plants, pruning overgrown beds and adding new varieties. We have focused on the Oak Allée as a place for adding new varieties of deciduous hollies. In the early 2000s, we propagated plants from the Rutgers University Gardens and Scott Arboretum, focusing on less common varieties of Altaclera, Koehne (I. × koehneana), and other hollies. More recently, we have focused our efforts re-propagating plants in our collection that are not held by other botanic gardens. 

Hollies have separate male and female plants (dioecious), so unless male plants are known to be in your neighborhood, you will have to plant both sexes to get good fruit-set. With so many beautiful varieties of holly it is difficult to recommend just a few. However, here are some suggestions to get you started:

  • American holly: a large plant, it can grow up to 50 feet tall. Numerous varieties include ‘Jersey Princess’, ‘Old Heavy Berry’, ‘Hedgeholly’, and ‘Jersey Knight’ (male).
  • Koehne holly: medium-sized, reaching 25 to 40 feet with beautiful chestnut-like leaves. Several varieties include ‘Lassie’, YULE BRITE, and ‘Chieftain’ (male).
  • Meserve hollies (Blue and China hybrids; × meserveae): include some of the most popular hollies available; most are relatively small, only reaching 5-6 feet in 5 years and 12 feet at maturity. Look for BLUE MAID, ‘Blue Angel’, GOLDEN GIRL, pollinated by ‘Blue Prince’; CHINA GIRL and CHINA BOY.

So if you are looking for a little touch of green this winter, come to the Arboretum and enjoy our Holly Slope. Hopefully you will be inspired to grow some of these wonderful plants in your own garden.