Betula nigra ‘Cully’ HERITAGE
Photo by Katherine Wagner-Reiss.

Contributed by Katherine Wagner-Reiss

Betula nigra ‘Cully’ HERITAGE  is a wonderful example of how the combination of serendipity and hard scientific investigation brings us important cultivars. Betula is the Latin word for birch. Nigra means black, and the bark of the straight species Betula nigra is almost black when mature. ‘Cully’ is the surname of the nurseryman who noticed a spectacular tree in the lawn of a St. Louis, MO home. While it looked somewhat like a Betula nigra, the bark was so white and papery that Cully thought that it might be a hybrid between Betula nigra (black birch) and Betula papyrifera (white paper birch). Extensive testing over a period of ten years revealed that it was not a hybrid, but a special Betula nigra, genetically endowed with ornamental peeling bark in hues of salmon, cream, and white; extreme hardiness; resistance to bronze birch borers; and the ability to grow in either waterlogged or dry soils.

In 1979, Earl Cully obtained a plant patent on this marketable ornamental tree and in the early 1980s he founded HERITAGE

Trees, Inc., thus explaining the trade name HERITAGE . If it seems somewhat odd to see a plant with trademark protection, consider that horticulture has a business component, too, which can help support additional and much needed plant research.

The common names for Betula nigra are black birch, red birch, river birch, and water birch. “Black’” and “red” refer to colors seen in the bark. “River” and “water” reveal that the native habitat for this tree is wet ground.

According to the Morris Arboretum Catalogue of Plants, the Arboretum has 25 of the straight species Betula nigra, 12 of the cultivar Betula nigra ‘Cully’ and one of the cultivar ‘BMNTF’ Dura Heat®. Until the leaves burst out this spring, enjoy beautiful birch bark. The locations of all of the birches at Morris Arboretum are mapped on Collection Connection.


Contributed by Lucy Dinsmore, Azalea Meadow Horticulturist 

Morris Arboretum’s mission has always championed staff development, and its leadership has encouraged and supported opportunities for staff to grow. There are two endowments that fund staff development, and there is a robust program that enables individuals across departments to pursue their professional goals which in turn furthers the goals of the Arboretum. Staff have opportunities to pursue conferences & symposia, higher education, plant collecting, staff exchanges, and international travel. Focusing on the last three, here are some examples that have enabled staff to advance their careers.

  1. Higher education – Many staff have achieved their graduate degrees at Penn while working full-time. Three horticulturists have received or are working towards their Masters of Environmental Studies. While the Arboretum’s endowments don’t fund these endeavors, the tuition benefit offered through the University of Pennsylvania is encouraged.
  2. Plant collecting – Plant collection trips go beyond the Executive Director and Director of Horticulture/Curator who’ve taken trips to China and Japan for plant research. Recently, Vince Marrocco, Chief Horticulturist, collected plants in Azerbaijan and Jess Slade, The McCausand Natural Areas Horticulturist, was encouraged to go on a collecting trip to North Carolina, joining representatives from a number of other institutions, including Longwood, Mt. Cuba, and Natural Lands. Plant collecting is an incredible way to see native plants in their habitats and create collections to add to the Arboretum’s portfolio. That experience is important in so many ways: it’s an introduction to other professionals and a chance to grow one’s network. And the outcomes of seeds collected are multi-faceted. When that seed comes back to the Arboretum, it becomes the goal of Shelley Dillard, Morris Arboretum Propagator, to grow them in the Greenhouse and then share them with other institutions. It’s a learning, teaching, and networking experience for Shelley and the Martha J. Wallace Plant Endowed Plant Propagation intern. Collecting trips involve a lot of sharing of information, positioning the Morris Arboretum as a leader in plant exploration.
  3. Transformational Staff Development - The Morris Arboretum supports staff exchanges and travel opportunities for staff and welcomes foreign colleagues alike. Here are a few examples. 

Botanical Scientist Cindy Skema will be traveling this summer to complete work researching the evolutionary history and systematics of an under-studied group of tropical plants, the Dombeyoideae (a subfamily of Malvaceae, particularly the genus Dombeya). The Arboretum is funding her travels to Paris to work at the natural history museum (Muséum Nationale d’Histoire Naturelle) with her colleague Dr. Timothée Le Péchon of Meise Botanic Garden. Cindy will maximize her collaboration to develop new research skills, particularly new lab techniques, which she’ll apply to the work on the flora of Pennsylvania. 

Assistant Director of Continuing Education & Penn Student Outreach Bryan Thompson-Nowak is doing professional development through a combination of funding from Morris Arboretum and the Chanticleer Scholarship (of which he was a recipient of in 2018). Last year, he completed a week-long executive education course with the Kellogg School of Management at Northwestern University where he learned about data analytics. Being in Chicago also allowed him the opportunity to meet with colleagues at the Morton Arboretum and Chicago Botanic Garden and discuss how they use data analytics in their business practices. He’s planning to extend these conversations this spring to colleagues in the UK with visits to Kew, Oxford, Cambridge, and the Royal Horticultural Society. He’s hoping to parlay this knowledge and utilize it at the Morris Arboretum.

In addition to Morris Arboretum sending staff on trips, it also hosts international institutions and individuals. One such example in 2018 was a visit from Japanese delegates from the Kobe City Government who, along with their host, Shofuso House and Garden in Fairmount Park, toured the Arboretum’s Japanese features with staff experts. Through a translator, they learned about some of the Arboretum’s history and features, and they in turn offered their experience and knowledge.

Lastly, several staff have benefited from the staff exchange program the Morris Arboretum has with Windsor Great Park. The Royal Landscape Exchange is a reciprocal staff exchange between Morris Arboretum and the Royal Landscape in Windsor, England. Now in its 7th year, the exchange allows horticulturists and staff from both institutions to travel and work alongside each other and share information, study plant collections, histories, learn about different tools and techniques, and immerse in another culture, climate, and landscape. I spent three weeks at Windsor Great Park in 2014, Jess Slade went in 2018, and in 2019, horticulturist Erin Conley will represent the Arboretum there.

During my rotation through the gardens, I worked alongside different horticulturists in the Savill and Valley Gardens, and visited numerous gardens, including a rose trial garden and the Royal Botanic Gardens, Kew, where I received a behind-the-scenes tour of their production and greenhouse facilities. Here, greenhouse staff showed us a unique contraption that they designed for woody plant propagation. For me, it was a paradigm shift learning their management and planting methods and preferred tools. Since then, we’ve modified our tool purchases toward more battery-operated styles.

Jess Slade with the Anckerwycke Yew, the National Trust's oldest tree. This 2,500 year old iconic tree stands at Runnymede in Windsor, England.


One of the highlights of Jess’ time in Windsor was visiting veteran trees with the park’s arboriculture team, including a 1,300-year old English oak, and learning how to read fungi growing on them as signs for management.  Jess shared that while much of the work was the same in England as in Philadelphia, for her, “meeting other professionals with a shared passion for the plant world and ecology was an unforgettable experience that shaped practices at home following the trip.”

As part of the exchange, Conor Langley, Horticulturist at Frogmore Estate on Windsor Castle’s grounds, spent time at the Morris Arboretum this past summer to see how public gardens are managed in the US and how native trees are cared for. He reported that he especially enjoyed helping to install the scarecrow exhibit along the Oak Allée, (commemorating Halloween in the US, which they do not have in England).

Travels like these are important ways of staying abreast of advances in the field. There is much to be gained from an exchange with another institution, whether it's in the Queen's backyard or midway across the country in Illinois. The information gained is key, both for Arboretum staff to disseminate what they’ve learned while traveling, and for sharing the wealth of knowledge that Morris Arboretum has with other institutions. Lastly, there is personal growth. These opportunities are about branching out, gaining perspective, and getting outside of one’s daily routine. Much like a sabbatical for an academic professor, these opportunities are also a way of pushing the reset button and recharging staff’s batteries.



Contributed by Daniel Sax, 2018-19 Walter W. Root Endowed Arborist Intern

It is with a heavy heart that the Morris Arboretum’s Urban Forestry team must announce an imminent loss to the University of Pennsylvania tree-scape. After much scrutiny, it has been decided that one of campus’s most distinguished Japanese zelkova (Zelkova serrata) specimens will be pruned to its base this coming spring. The tree in question was planted in 1971 as part of John Collins’ firm, Collins and DuTots’, design for the Hi –Rise, or ‘Superblock,’ residential development complex from 38th to 40th Street Walnut to Spruce. Collins –known locally for his work on the Schuylkill River Park project as well as the creation of Temple University’s Landscape Architecture and Horticulture programs–was renowned for his ability to integrate place and community through landscape design. It comes as no surprise, then that his choice to highlight the zelkova as a focal point of the College House green has been so successful; not only for the experience of visitors, but for the tree itself. Since its planting, the zelkova has thrived: growing to a trunk diameter of 33 inches and asserting itself as a dominant presence both when in leaf and during the winter months. Recent years have proven difficult for the zelkova, however, and, regardless of its impressive stature and historical pedigree, the tree has started to present structural red flags that cannot be ignored. For safety reasons, the canopy of the zelkova will be removed during spring break when fewer people are on campus.

The original landscape planting plan is shown above. The zelkova that is being removed is shown in green. On the left is the original corresponding planting plan.

The landscape architect, John Collins

Due to the constant pressure of torsional wind load –powerful gusts that twist the tree and its branches –significant cracks have formed along the zelkova’s primary branch unions. Although trees can typically adapt to such forces, this specimen has failed to do so, and the observed fractures have spread downwards towards the base of the trunk. In addition to these signs of stress, subsidence cracks –long fissures that run through the center of lateral branches –riddle the tree’s crown and have brought the stability of the zelkova’s branches into question. In short, the risk to students, faculty, staff, and Penn Arboretum visitors is too great to leave this heritage tree in its current state; however, there is still hope for its future.

Rejuvenation is a common tactic employed by urban foresters to mitigate risk to the public without sacrificing the totality of ecological services that a long-lived tree provides. When reduced to its base, the zelkova will respond with rapid shoot growth to compensate for the loss of its crown. As these pseudo-saplings develop, the most vibrant members will be selected by Penn’s consulting arborists and allowed to grow without competition. In time, an entire new canopy will emerge, once again providing beauty and shade to the Gregory College House. In the meantime, be sure to stop by to watch as this experiment in arboriculture begins!


Contributed by Katherine Wagner-Reiss

Cedrus atlantica ‘Aurea’ at Morris Arboretum. Photo by Katherine Wagner-Reiss.

Is Cedrus atlantica native or non-native to Pennsylvania? The answer is easy if you know that there are no native Cedrus trees (cedars) in North America; this is a non-native evergreen from northern Morocco and Algeria.

What does the botanical name tell us? Cedrus is the Latin name for a cedar.  The specific epithet atlantica can mean either of/from the Atlantic Ocean or of/from the Atlas Mountains; in this case it means the latter, thus the common name for this tree is Atlas cedar.

Ten Cedrus atlantica are found in the Morris Arboretum Catalogue of Plants: six of the straight Cedrus atlantica species (Atlas cedar), one Cedrus atlantica ‘Aurea’ (Golden Atlas cedar), two Cedrus atlantica ‘Glauca’ (Blue Atlas cedar), and one Cedrus atlantica ‘Green Wave’ (Green Wave Atlas cedar).

That ‘Aurea’ means golden is easily understood when you recall that the chemical symbol for gold is Au. ‘Glauca’ means “having bloom.” Bloom is a white-grey powdery coating of wax, which can occur on the surface of leaves or fruit (such as plums). Bloom causes leaves to have a bluish-grey or bluish-green appearance, thus explaining why the common name for C. atlantica ‘Glauca’ is Blue Atlas cedar.  If you are going to purchase a specimen, be aware that the needle-like leaves of this cultivar can range in color from silvery blue to dark green, so be sure to choose the hue that you like best.

Cedrus atlantica ‘Glauca’ at Morris Arboretum. Photo by Katherine Wagner-Reiss.

‘Green Wave’ deserves a paragraph of its own because it is a cultivar that originated as a witches’ broom (a genetically altered branch) on a 100-year-old C. atlantica ‘Glauca’ (1932-0303*A) growing at Morris Arboretum! ‘Green Wave’ is remarkable for its sculpted form and dwarf habit; it grows only 3-6 inches per year to reach an ultimate height of 4 feet. Species C. atlantica can grow to 60 feet!

Cedrus atlantica ‘Aurea’ is particularly easy to find at Morris Arboretum because it is located adjacent to the Katsura tree. You can find the exact locations of any of the Atlas cedars on the Arboretum’s Collection Connection. Luckily, these massive and long-lived trees are being conserved in botanical gardens as they are endangered in their native habitats.

Fun fact:  You will not find decorations made of cedar cones because female cedar cones disintegrate on the bough, dispersing their seeds to the wind, rather than falling intact to the ground.


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