Enjoy this summer edition of "Dogwood Lane" that explores Polly Wakefield's work to create and patent new kousa dogwood cultivars

Dogwood Lane

The Quarterly Journal of the Mary May Binney Wakefield Arboretum ___________________________________

Volume Four, Issue 4 - Summer 2022

Polly Wakefield's work to create, patent, and name new kousa cultivars

Thousands of new plant varieties are introduced each year all over the world. New plant introductions occur for a multitude of reasons that include: use in agriculture, forestry and industry, medicine, aesthetic interest, and conservation. Polly Wakefield worked for forty years breeding and selecting Cornus kousa (Asian Dogwoods) cultivars to be introduced into the nursery trade. These trees showed a variety of unique characteristics that included large and distinct flowers (bracts), lustrous leaves and fruit, and cold, drought, and disease tolerance. Many of Polly’s cultivars can be found in the nursery trade to this day.

Before getting into greater detail about Polly’s work with this species it may be helpful to review relevant plant terminology that can be confusing even to the professional horticulturalist. Using the Cornus kousa as an example: Cornus is the family. Cornus kousa is the species. A ‘variety’ is a variation within a species that has arisen naturally. The native range of Cornus kousa is Asia. Therefore varieties of Cornus kousa are native to Asia. In 1907 seed from the Cornus kousa chinensis, the Chinese dogwood, was collected for the Arnold Arboretum by E.H. Wilson in Ichang, western Hubei province, China. He believed it would probably prove better to cultivate than the Japanese variety. For her work with dogwoods, Polly collected seed from two Arnold Arboretum plants: Cornus kousa 'Viridis', grown from seed that had been collected in the wild by E.H. Wilson and propagated at the Arnold Arboretum; and an unnamed cultivar from Skylands Nursery in New York.

Cultivars are specific individual plants that have been cultivated by humans for certain characteristics. For these characteristics to remain ‘true’ (meaning specific individual plants should have characteristics that stay the same from one generation to the next) and consistent, it usually requires cloning or cuttings. They cannot be reproduced by seed as a general rule. When cross-pollination occurs between two plants, hybridization results, and the offspring usually bear characteristics distinct from either parent. Hybridization can occur between different cultivars within a species, sometimes resulting in a new and distinctive cultivar. This new cultivar often has characteristics that are desired by humans including bigger flowers, longer or unusually shaped leaves, and large fruit.

As we've detailed in earlier editions of Dogwood Lane, Polly often visited the Boston Public Garden as a young woman. At the time, the garden had been fashioned into an arboretum boasting six hundred trees of thirty kinds. She described the collection in her article, "The Boston Public Garden" published in the Arnold Arboretum's journal Arnoldia; it included "two hundred elms (American, English, and Dutch), nearly one hundred maples, fifty magnolias and willows, fourteen crab apples and catalpas, eleven horse-chestnuts, seven varnish trees, and specimens of Kentucky coffee tree, locust, beech, larch, tree-of-heaven, cherry, plum, peach, laburnum, oak, and ash. The ground was found to be too marshy for evergreens other than rhododendrons, so the other shrubs used included deciduous lilacs, quinces, mock oranges, and viburnums."

In the period after her graduation from Lowthorpe School with a degree in Landscape Architecture, young Polly Binney embarked upon what would be scores of classes at the Arnold Arboretum, many of which were about Plant Propagation. The classes began with a seed collection walk, highlighting several species that are well-suited to grow from seed after hot or cold stratification. Different species rely upon these periods of cold (generally in the form of winter) followed by a warmer period in order to germinate. In her Arnoldia article about Dogwoods, Polly acknowledges that in 1956 she attended Propagation 1 taught by Roger Coggeshall and that they collected fruit including dogwood fruit at the summit of Bussey Hill. She chose the largest fruit from a "round-headed tree." She also added that she continued to take that same plant propagation course for a number of years.

A glance at early editions of Arnold Arboretum's frequent publication Bulletin of Public Information (later known as Arnoldia) reveals what an exciting fairyland the arboretum must have been in the first half of the twentieth century, offering an opportunity for everyday visitors to see exotic plants unlike any they'd ever imagined, and fueling a burning hunger in budding plant collectors and hunters. The bi-weekly publication, which tracked the bloom and enticing display of the Arboretum's collection must have read like a nursery catalog of "must haves" to these individuals. They include some of our sylvan treasures such as Acer griseum, Parrotia persica, Cercidiphyllum japonicum, Styrax, Cornus mas, Cornus controversa, Albizzia julibrissin, Acanthopanax, Prunus, and Stewartia species, as well as many of our most popular shrubs such as Kolkwitzia amabilis, Enkianthus campanulatus, Kalmia latifolia, Rhododendron vaseyi along with other rhododendrons, lilacs, clethras and mock oranges. During that time, Polly was propagating many of the plants aforementioned in addition to kousa dogwoods, growing them to add to her Milton Garden. It is truly remarkable to see how many of the species mentioned Polly would later propagate and/or acquire at one of the Arboretum's annual plant sales to add to her growing collection. Many of these now fully complement our kousa collection. These propagation classes at the Arnold Arboretum would also empower her to start to build her own collection by growing dogwoods and other plants from seed.

One of the earliest mentions of the kousa dogwoods in Arnold Arboretum's collection is this tantalizing entry by E. H. Wilson that appeared in this Bulletin of Public Information in 1930 (and is cited by Polly in her Arnoldia article A Fascination with Dogwoods):

"Cornus kousa chinensis, the Chinese Flowering Dogwood, is now in perfect bloom in the border devoted to the newer Chinese plants on Bussey Hill. The specimen is a vase-shaped bush about 18 feet tall with a spread of 15 feet; the branches are numerous, ascending-spreading with relatively slender secondary branches which give off innumerable short, lateral branchlets each of which terminates in a solitary flower head. The flowers proper are an insignificant crowded mass subtended by four, creamy white bracts, ovate and pointed and overlapping at the base, forming a cross some 3 to 4 inches in diameter. The leaves are fully grown when the flowers are open and are opposite, lustrous green, lanceolate-ovate, each from 3 to 5 inches long, somewhat leathery in texture, dark green above and pale on the under surface. The new shoots are purplish. The fruit is a conglomerate mass singularly resembling a strawberry. The bracts as they open are greenish and from the time they begin to change to white until they fall is a period of about a month, so for at least three weeks, this plant is a mass of white. It blooms just as freely as the native C. florida and has the advantage of a foil of green leaves below the inflorescences, moreover, its blossoms open when those of the native species are passed. A native of the margins of woods and thickets of central China between elevations of from 4000 to 8000 feet, the Chinese Flowering Dogwood was introduced into cultivation by E. H. Wilson in 1901; it has proved perfectly hardy in the Arboretum, where it has been growing since 1907. The late Professor C. S. Sargent considered that of lesser trees this Dogwood was one of the greatest gifts of the Orient to the gardens of eastern North America. At the moment it presents a lovely picture worth coming a long way to see."

Referring to this as a kousa dogwood flower is incorrect - it's actually an inflorescence.

Wilson describes the kousa's tiny actual flowers shown here in the middle of the bract: "The flowers proper are an insignificant crowded mass subtended by four, creamy white bracts, ovate and pointed and overlapping at the base, forming a cross..."

This was an exciting time in horticulture, and the Arnold Arboretum was instrumental in many important plant introductions. In 1953, the first International Code of Nomenclature for Cultivated Plants introduced the term "cultivar" to cultivated plant taxonomy. Key players including the Arnold Arboretum were urging "nurserymen" to address the need for new introductions, improvements, and enhancements with troubled and/or popular species. Cornus kousa was easy to propagate from seeds and cuttings and produced flowers in 3 to 4 years. The Cornus kousa was also relatively rare in American gardens at the time and Polly saw the incredible potential in this wonderful ornamental plant. With her success at the propagation of plants, land ripe for nurseries, and strong associations with key figures, Polly embarked on a project to nurture, identify, and select new kousa dogwood cultivars worthy of distinction. She sought to impact and improve the species by carefully collecting seed from distinctive mother plants. Polly and her contemporaries like Polly Hill must have relished the idea of identifying an outstanding new plant that had grown serendipitously from seed collected from just the right plants. Who wouldn't want the privilege of naming their own precious plant? Many of the plants Polly had learned about or admired honored the discoverer in their names such as Davidii and Wilsonianii.

Spurred by this exciting challenge, Polly vigorously pursued her interest in propagating unique kousa cultivars and set out at the home in Milton to experiment with growing trees from cuttings, thus ensuring their genetic purity.

In 1972, Arnold Arboretum Chief Propagator and renowned plantsman Al Fordham recounted Polly's efforts (though leaving her anonymous) in his talk to the International Plant Propagators and published an article in American Nurseryman entitled "Cornus Kousa and Its Propagation":

"In the early 1950's an amateur horticulturist in the Boston area obtained seeds of the C. kousa var. chinensis from the Arnold Arboretum and started a collection of plants. They were lined out orchard fashion in a field where they could be observed. From time to time more were added and the planting now contains more than 150 specimens."

He continued, stating that much of the information he was presenting was based on observations from that collection. It is apparent from this piece that, at the time, the Kousa dogwood was not a commonly known or available species. Yet there was a tremendous amount of interest and curiosity about the species spurred by remarks like Fordham's opening line: "Cornus kousa, the kousa dogwood, is one of the most outstanding and trouble-free trees available to horticulture." He highlighted its hardiness and month-long display, "a profusion of flowers with showy white bracts." In his talk, Fordham shared information about variation in the characteristics of the flowers, variation in the fruit, seed dispersal by wildlife, and propagation by seed and cuttings. He ended with the recommendation that those interested in Cornus kousa should select clones that combine the more desirable traits and provide them with cultivar names, adding an "ideal plant would exhibit good floral characteristics when viewed from eye level, large bright red fruits, pleasing autumn color, and prominent exfoliating bark."

Some of the amazing variations of kousa bracts from Polly's plants grown from seed.

In Polly's notes, she described how the fascinating and exciting process of working with Fordham had evolved, "Three years ago Alfred Fordham of the Arnold Arboretum came to see me and I showed (my kousa seedlings) to him. He was interested in them and came again to photograph and document the variety. (He) tagged several of outstanding flower and tree form. (He) came again and took cuttings and herbarium specimens from some. But the one that held its cup shape was the one that impressed visitors most. He has returned each year - others of the Arboretum staff have come too. Mr. Fordham has taken cuttings and herbarium specimens of some but not given any away and will not. Last June, he took slides to a meeting of the International Plant Propagators and showed them to prove how much variation there is when plants are grown from seed. When the multibracted one was shown, Bill Flemer (of Princeton Nurseries) said a murmur went up in the audience -- they did not seem to have seen one before." Fordham also worked with her on this collection and advised her on which attributes to monitor, while familiarizing her with the process of developing her own cultivars for naming. In addition to the qualities Fordham had highlighted, Polly was keen on selecting plants that were particularly cold hardy, and drought tolerant due to great variations in the New England climate at the time of her work.

Armed with a collection that she had grown from seed and observed over several years, expert selection input from Fordham and several other Arnold Arboretum experts, and notoriety from their speeches and publications, Polly began the process of naming and cloning special specimens in her planting. Several of these were proving sufficiently unusual that the prospect of patenting was warranted.

Polly chose to work with the kousa dogwood for many reasons. Most importantly she fell in love with the plant referring to it as: “one of the most outstanding of all flowering trees that will thrive in the changeable New England climate. Ornamental at every season of the year, these seedlings never cease to astonish me with their vigor, their hardiness, and most particularly their individuality.” According to Polly, an important detail was the way the Cornus kousa carried its flowers.“ They may be born singly on short horizontal branches or they may appear in lines of five to eleven flowers along the top of the branches creating the impression of being laden with snow.”

Mary May Binney Wakefield Arboretum's kousa dogwoods with "snow laden" branches of flowers

In her 1990 article printed in Arnoldia "A Fascination with Dogwoods," Polly shared what she considered a notable example of this: ”One particularly important distinction in this regard is whether or not the tree can be classified as “upstairs” or “downstairs” trees. As I define it, an upstairs tree, because it holds its flowers along the upper side of its branches, is best viewed from above. A downstairs tree, on the other hand, produces flowers that are somewhat turned down and are best viewed from ground level." (Editor's note: It is worth noting that Polly would create the ideal formal garden in which to view "upstairs" trees. During dogwood bloom in June, the Mary May Binney Wakefield Arboretum's descending terraces allow visitors to look down onto Polly's dogwoods from the top terrace and marvel at the stunning display of the "upstairs" trees before stepping down into the garden to enjoy the "downstairs" variety with their snow-laden-like cascades of dogwood bracts.)

Flowers of an "upstairs tree," facing upwards and best viewed from above

Flowers of a "downstairs tree,"

best viewed from ground level

Polly and the Patent Process

After growing over 150 plants and their progeny at her home in Milton in orchard fashion for 3 or more years to the age where they had flowered, Polly had identified some trees that were true standouts. She "selected" these plants because she could argue they were in some way spectacular, new and distinct, and worthy of naming and perhaps even patenting. She described the process in the first section of her patent application: "The present invention relates to a new and distinct variety of dogwood tree of the Japanese dogwood type botanically known as Cornus kousa, which was originated by me from a seed which was initially processed and then planted by me indoors in my house, and then set out as a young seedling plant in my nursery located at Milton. When I acquired this seed, I was attending classes on plant propagation conducted at the Arnold Arboretum. My interest in plant propagation and experimentation led me to seek and receive permission to obtain seeds from various plants, including dogwoods, being grown at the Arboretum. This particular seed was taken by me from the largest-fruited dogwood tree specimen of the kousa type which had attracted my attention, but which was of uncertain origin and parentage."

Above, 150 kousa dogwoods planted orchard style. Below, the fastigiate habit of "Twinkle."

For each application, she notes what made that particular tree stand out. For example, for the plant she named Venus/Silver Star she stated, "In a few years, I observed that my new seedling had an unusual vase-shape and flowers were unusually wide-bracted and somewhat cupped, without ever becoming flat...with flowers that bloom later and longer than almost any other variety." Once she identified a plant's noteworthy attributes, she would asexually reproduce it from rooted cuttings. Further, she had to "assert a claim on its behalf" such as, in the case of her second patented cultivar known as 'Twinkle', she claimed its fastigiate habit, unusually large flowers, and their tier-like arrangement made the variety one of the most beautiful, unique, and valuable Japanese dogwoods she'd ever seen. The application was a lengthy document requiring a full description of the new plant, its unique characteristics, and features along with details about its foliage, bark, flower buds, flowers, bracts, fruit, and fall color. The Washington DC-based patent and trademark law firm Robb and Robb prepared five plant patent applications in the early seventies and presented Polly with their patent certificates. (Polly's patents and a significant collection of related documents are accessible for view and research upon request and appointment at the Massachusetts Historical Society(MHS). Request the papers of "Wakefield, Mary May Binney, 1914-2004. Papers, 1900-2005.")

Upon their certification, industry publications announce new patented cultivars and soon Polly was receiving inquiries from individuals and nurserymen interested in acquiring scions (cuttings) to root and sell. Polly was enthusiastic about sharing her scion wood and anxious to hear of the plants' results, "As for me - well no mother could be more interested in her children's prowess than I in my kousa selections, so keep me informed." Several nurseries and individuals chose to focus on kousa dogwoods, like Polly, in hopes of producing the best dogwood available. Some of Polly's named selections, though not patented, garnered great interest in the trade including 'Greensleeves', 'Moonbeam', and 'Moonlight'. It is a mystery why she didn't pursue additional patents for some of her other "named" cultivars, most notably 'Greensleeves', mentioned in Paul Capiello's "Dogwoods: The Genus Cornus" as being perhaps the best kousa dogwood cultivar available. Pursuing patents for all her named cultivars may have simply proven to have become a larger-scale proposition than she'd bargained for.

Clues that this may have been the case can be gleaned from the flurry of related correspondence found in the Wakefield archives of Polly's papers (at MHS as mentioned above). The documentation required for each patent was exhaustive and required careful written and photographic records of the specimen depicting its unique characteristics throughout the year (In the letter at right, Polly describes trudging through the snow to document the branching habit of her plants). While her first patent came through in 1972, fifty years ago this month, she was deeply immersed in process of compiling her five patent applications for over five years.

During this time, the buzz about her trees was generating other attention and inquiries. One such letter came from Betty Powell in 1974 when she was compiling a book "The Avant Gardener, a handbook and sourcebook of all that's new and useful in gardening." Powell informed Polly that her "new patented dogwoods would be described in the section on trees." In her reply, Polly singles out her 'Silver Star' (described by Polly later in this text) as well as her 'Moonbeam', stating it is "so beautiful people always stop and exclaim. When it is opening the center part is greenish and gives it a lovely quality as if the flowers look at you." She mentions that others were not yet named as they were attempting to "secure a quantity grower and consult him about good names."

After a busy period in her life in the 1980s, the death of her husband in 1988, and a revival of interest in her work with Cornus kousa sparked by her Arnoldia piece in 1990, Polly now seriously explored marketing and trademarking her cultivars. She was in correspondence with Stephen Spongberg of the Arnold Arboretum who was then in charge of the International Registry of Cultivar Names, but nothing was added by him.

In her notes, she jotted down that one of her nurseryman collaborators had explained, "trademark protects the name, a patent protects the plant." She also considered changing the names of her cultivars to include "Maryfield" in the plant names, for example, 'Maryfield's Silver Star'or 'Maryfield's Moonbeam', remarking that it was "our name for this place." She was in correspondence with several key nurseries that specialized in kousa dogwoods and who were interested in carrying her cultivars. She provided scions to these nurseries so that they could grow them from the rootstock and report back to her about how they fared with the intention of selling her cultivars for which she would get a small royalty. In the archives of Polly's documents, some of this correspondence has been especially insightful given the recent and challenging climate issues impacting our collection. The Handy Nursery in Oregon reported to Polly about which of the cultivars were performing the best, remarking that they'd experienced the worst drought ever, going without rain for months. Many of the dogwoods had been left scorched by the heat and drought, but that 'Greensleeves' had fared the best.

Polly Wakefield's cultivars 'Moonbeam' and 'Moonlight' from Andre Gayraud's book Cornus

The Handy Nursery, Broken Arrow Nursery, and others requested descriptions for their catalogs, and her write-ups are illuminating as Polly had now worked with these cultivars for over twenty years. (After observing Polly's collection for fifteen years, especially the "keystone" plants she placed in prime locations, the Mary May Binney Wakefield Arboretum staff may be able to match up these key plants with these descriptions, the patent applications, and the historical documentation from this period to make well-informed guesses about which named-cultivar they are, at some point even attempting to make a DNA match. We especially suspect that the magnificent tree near the entrance is a 'Silver Cup'. Each year it provides an amazing show with its cup-like flowers and its prominent location at the corner of the lane and entry drive.)

This magnificent tree near the Wakefield Arboretum entrance and Carriage Barn dazzles visitors each year with its overwhelming and long-lasting blooms. It is likely Polly's named but not patented cultivar C. Kousa 'Silver Cup', most distinctive because of its unique cup-like persistent bracts (shown above at right.) The tree's impressive bloom, each year consisting of thousands of bracts, is shown at in the picture at left- the stunning tree to the middle and right of the frame.

Polly's notes describing her named cultivars (noting the patent numbers and dates on those patented) - text created for use in nursery catalogs.

A photo taken in the 70's documenting the significant variance in fruit size of the various cultivars.

One of Polly's first patents for her named cultivar 'Twinkle' issued fifty years ago this week.

The Impact of Anthracnose on Cornus florida

When Polly was pursuing her work propagating dogwoods, the native dogwood (Cornus florida) was being severely impacted by anthracnose, a devastating disease. Polly was well aware of this issue even referring to the devastation it caused the native Cornus florida in her Arnoldia article from 1990. A companion article in that issue detailed how something unusual began to happen to the flowering dogwood (Cornus florida) during the late 1970s. Cornus florida, one of eighteen species of Cornus native to the United States, began to decline in parts of the Northeast due to a new fungus disease, dogwood anthracnose (Hibben and Daughtrey, 1988).

Once impacted by the fungus, well-established trees would experience branch dieback and the leaves would reveal purple and brown spots and blotches on the leaves that would sometimes expand until the entire leaf was blighted. According to Nicholas J. Brazee of UMass Amherst, dogwood anthracnose, or Discula destructiva, was introduced into eastern North America from Asia in the late 1970s and quickly spread throughout the region, decimating natural populations of flowering dogwood in southern New England.

Because D. destructiva is non-native in North America, flowering dogwood has no natural defense against the pathogen, allowing the fungus to spread unchecked within the tree. Under ideal environmental conditions, dogwood anthracnose can be the sole cause of death. The Cornus kousa was unaffected by the disease. The Arnoldia article also shared insights about how the fungal disease was spread by wind-dispersed spores and that since these trees are especially vulnerable to periods of drought because of their shallow root systems, it recommended supplemental watering during extended rainless periods but cautioned that "overhead sprinklers should be avoided because wet foliage is more likely to become infected." Polly's elaborate nursery setup utilized an overhead irrigation system to combat severe drought in 1987 and 1988 and irrigate her recently transplanted kousas. She feared that her use of the overhead system overnight unwittingly created conditions that were favorable to the spread of dogwood anthracnose, prompting her to stop night watering, remove most of her C. floridas from her nurseries, and focus exclusively on C. kousas. Her affinity to the Cornus family, especially Cornus florida, had first been established during her work with the Garden Club of America's Blue Star Highway initiative. Nationwide, these efforts included plantings of thousands of Cornus floridas lining newly created interstate highways (for more info, read our winter edition of Dogwood Lane). To read more about dogwood anthracnose, click here.

BOOK OF THE QUARTER:

Wild Trees by Richard Preston

Each quarter we will suggest a new book that focuses on topics including horticulture, climate change, ecology, and the intersections of humans and nature. At the end of the quarter, a presentation will be given on the book and readers will be asked to participate in the conversation about the topic.

Richard Preston's Wild Trees explores an Eden far above the forest floor in the canopy of Sequoia Sempervirens, coastal redwoods that include mosses, ferns, blackberry bushes, and an array of wildlife beyond imagination. Until fairly recently the tops of these trees were unexplored. Thick layers of soil sitting on limbs harbor plant and animal life previously unknown to scientists. In Wild Trees, a group of young adventure-seeking botanists overcomes many obstacles to ascend hundreds of feet and share the secrets of the largest single living organism on earth.

This book will provide the backdrop for a follow-up zoom discussion of the book later in the quarter. Our September e-newsletter will provide schedule information for this session.

We want to hear from you! We appreciate your feedback about our quarterly. Please let us know what research and articles you have found most interesting.

Articles written and edited by Erica Max, Debbie Merriam, and Mark Smith.

Layout by Erica Max and Debbie Merriam.

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