The Gardens

Longwood Cannas (Canna)

Prior to the 1960s, cannas were used primarily in formal Victorian gardens. There were few color choices, and they generally grew to six feet or taller. Dr. Robert Armstrong, Longwood’s Geneticist, began the canna breeding program in 1967, when it was realized that cultivars available at that time were not suitable for use on display in the Gardens. The original goal was to develop a clear yellow-flowered dwarf canna and a pure white-flowered canna that could grow well in the Conservatory. The project started with making crosses involving three cultivars, ‘Ambassador’, ‘Moonlight’, and ‘Banner’, which were obtained from Yalta, Ukraine and South Africa. As the project progressed, other cultivars and species were introduced from around the world. Seeds of five species were received from Lago Maggiore, Italy, Canna glauca was procured from Rio de Janeiro, Brazil, and in 1972, Dr. John Creech of the US National Arboretum, added three Russian cultivars, ‘K.A. Timirazov’, ‘Krimsky Riviera’, and ‘Soleznaya Krasavaya’. With the new additions to the breeding stock, red, orange and pink cannas were developed for the Conservatory along with the original white and yellow. The selection criteria used were plant vigor, early flowering, foliar appearance, self-cleaning ability and good propagation qualities. Between 1972 and 1985, twelve cultivars were selected for release. Named for local historically significant places and events, they were: ‘Brandywine’, ‘Chesapeake’, ‘Conestoga’, ‘Constitution’, ‘Declaration’, ‘Delaware’, ‘Franklin’, ‘Freedom’, ‘Independence’, ‘Liberty’, ‘Lenape’ and ‘Penn’.

Another project was to breed aquatic cannas. Canna glauca, which has roots that tolerate being submerged in water, was crossed with the terrestrial hybrids. Four cultivars, ‘Endeavour’, ‘Erebus’, ‘Ra’ and ‘Taney’, all named after famous ships, were selected in 1972. In 1990, Hawaiian-themed cultivars ‘Aloha’ and ‘Pele’ were released. Today at Longwood, cannas are used extensively in the Conservatory, Flower Garden Walk and Idea Garden.

Longwood New Guinea Impatiens (Impatiens mooreana, Impatiens herzogii, Impatiens linearifolia, Impatiens schlechteri)

New Guinea Impatiens were originally discovered in the late 1800s. They were introduced into the US in 1970, when Longwood Gardens and the US Department of Agriculture (USDA) made a joint plant-collecting trip to New Guinea. Longwood funding provided the opportunity for Dr. Harold Winters and Dr. Joseph Higgins of the USDA to spend ten weeks in New Guinea collecting plants. The main goal was to collect tropical rhododendron species, but there were many other plants on their list, including impatiens. They found an enormous variety of impatiens all over the country and were able to transport some back to the US. Dr. Robert Armstrong, Geneticist at Longwood Gardens, received samples of the collected plants and began a breeding program. Some crosses were made to increase flowering and to find the best flower color and foliage.

In 1974, Longwood distributed the Circus series, which included 10 cultivars, ‘Bozo’, ‘Carousel’, ‘Harlequin’, Cotton Candy’, ‘Lollipop’, ‘Big Top’, ‘Charmer’, ‘Orange Crush’, ‘Painted Lady’ and ‘Stop Light’. These cultivars were selected mainly for their flower color, floriferousness, and good quality foliage. Subsequently, more cultivars were developed in the Circus series, which included ‘Calliope’, ‘Cannonball’, ‘Fortune Teller’, ‘Chariot’, ‘Juggler’, ‘Magician’, ‘Ringmaster’, ‘Roustabout’, ‘Showboat’, ‘Trapeze’, ‘Carnival’, ‘Headliner’, ‘Majorette’, ‘Roller Coaster’, ‘Ringmaster Improved’ and ‘Skyrocket’. Longwood ended this breeding program in 1978, because by then many commercial growers began working on impatiens breeding and there was no need to duplicate these breeding efforts. Although the original selections of Longwood’s impatiens are not generally used in the Gardens currently, newer varieties of New Guinea Impatiens can be found each summer in the Idea Garden.

Hollies (Ilex)

Hollies have been an important part of Longwood Gardens since the time of founder Pierre S. du Pont. From the beginning, he collected interesting specimens. This tradition has been continued by Longwood’s staff through seed exchanges with neighboring gardens and plant exploration around the world. Longwood currently has 318 active holly accessions in the garden. Approximately 100 of these are located in the Experimental Shrub Trials to determine their display value.

Ilex opaca ‘Longwood Gardens’

Pierre S. du Pont, Longwood’s founder, collected plants that added distinctive touches to the garden. Mr. du Pont’s brother-in-law, F. L. Belin, purchased several yellow-berried American hollies (Ilex opaca) from an unknown man. Upon seeing these plants in Mr. Belin’s garden, Mr. du Pont liked them so much and requested some be sent to him. Subsequently, one of the larger hollies was transplanted to Longwood. This plant is now located on the east side of the Open Air Theater. 'Longwood Gardens' can also be found in the Idea Garden and near the Terrace Restaurant. Mr. du Pont made cuttings available to nurseries and this form of Ilex opaca named ‘Longwood Gardens’ has been available in the nursery trade since the 1950s.

Ilex x attenuata ‘Longwood Gold’

Longwood originally received this yellow-berried holly in the early 1970s as an open-pollinated seed from Morris Arboretum in Philadelphia. The plant was obtained believing that it was a rare holly species, Ilex forrestii, native to East Tibet and China. When this plant was grown, it was identified as Ilex x attenuata, a natural hybrid of two North American species (Ilex opaca and Ilex cassine). Morris Arboretum later re-identified the tree from which the seed was collected as Ilex x attenuata ‘Fosteri’. They suspect that it was a simple typing error that changed the name to Ilex forrestii. One of the plants grown from the seed received from Morris Arboretum turned out to have yellow fruit and Longwood selected this plant in 1976 for its fruit color and superior cold tolerance.

Ilex serrata ‘Longwood Firefall’

This red-berried shrub has a small form, growing to about 6’ tall, and gives a spectacular show of color in the fall. Obtained by Rick Darke, then Curator of Longwood Gardens, and Sylvester March of the US National Arboretum in 1985 from Shimabichi Nursery in Kawaguchi, Honshu, Japan. Selected for its semi-pendulous habit, it was named and introduced by Longwood Gardens. This plant was distributed in 1999 to nurseries and is commercially available.

Clivia miniata ‘Sir John Thouron’

This rare yellow-flowered clivia was named for Sir John Thouron, who gardens at Glencoe Farms in Pennsylvania. Sir John received this plant from Queen Elizabeth II in Scotland many years ago and brought it to Philadelphia in the 1950s. Longwood Gardens facilitated the naming of the cultivar and distribution of this plant. In the early 1990s, White Flower Farm, a retail mail-order company in Connecticut, made the first commercial offering of this clivia and sold 36 plants for $950 each. On several occasions, a plant has been in the annual Rare Plant Auction held by the Delaware Center for Horticulture, and it has raised over $1,000 each time. Mrs. Lammot du Pont Copeland entered one in the Philadelphia Flower Show in 1999 and received the Pennsylvania Horticultural Society award of the highest-scoring blue ribbon entry. Longwood continues breeding this plant to find a double-flowered clivia.

Corylopsis glabrescens ‘Longwood Chimes’

In 1983, Dr. Clifford Parks of the University of North Carolina at Chapel Hill collected seeds of Corylopsis glabrescens on the Ebino Highland in southern Kyushu, Japan. The seeds were then distributed to the US National Arboretum and in 1985 Longwood Gardens received three seedlings from that Arboretum. Of these three, one seedling was selected as an outstanding specimen for the Gardens, because it has flowers and inflorescences larger than typical for this species. Its flowers are exceptionally fragrant and open about two weeks later than most other corylopsis. This cultivar was named ‘Longwood Chimes’ because the original specimen grows near the Chimes Tower in the Gardens. At an auction at Philadelphia's Morris Arboretum, this plant was up for bidding as a Garden Treasure. This plant has been distributed to nurseries in 1999 and is commercially available.

Magnolia acuminata var. subcordata 'Peirce's Park'

A yellow-flowered magnolia, known at that time as Magnoliacordata was planted on the Peirce farm (what later became Longwood Gardens) by Joshua and Samuel Peirce. This magnolia was discovered in 1788 by French explorer André Michaux in South Carolina. Michaux was the author of one of the first floras of North America and was one of the first trained botanists to explore and collect plant specimens in the Southern Appalachian Mountain region. The Peirce brothers most likely procured this magnolia from Michaux, with the help of either John Bartram or William Hamilton, owners of two prominent Philadelphia gardens. The tree still stands at Longwood Gardens, south of the Peirce du Pont house, and is a national champion at about 100’ tall. This clone was given a cultivar status because of its historical significance. This plant was distributed to nurseries in 1998 and is commercially available.

Rhododendron ‘Pierre du Pont’

In 1927, Pierre S. du Pont, founder of Longwood Gardens, constructed a greenhouse on the present site of the East Conservatory to house du Pont’s collection of azaleas and rhododendrons. There were two major collections, the first, one of the largest and finest collections of Belgium azaleas in the country; and the second, a rhododendron and azalea collection previously belonging to Professor Charles Sprague Sargent, Director (from 1873 to 1927) of the Arnold Arboretum in Boston. The two collections were found among other rhododendrons and azaleas that du Pont had obtained. This greenhouse was known as the Azalea House and sheltered the azalea collection until 1983 when it was replaced by the East Conservatory. One rhododendron that is still found in the Conservatory is Rhododendron ‘Pierre du Pont’. This plant was Mr. du Pont’s favorite azalea. It is thought to have been obtained in the early 1920s from an estate in Massachusetts that was being broken up.

Sorbus rufoferruginea 'Longwood Sunset'

In 1964, Longwood received a seed of this plant from Mrs. Polly Hill of Martha’s Vineyard, Massachusetts. Mrs. Hill originally received the seed from Dr. Tsuneshige Rokujo, of Tokyo, Japan, who had collected the seed from a tree in cultivation there. In the 1950s, Mrs. Hill founded an arboretum in West Tisbury, on Martha’s Vineyard, known today as Polly Hill Arboretum. Over the years, Mrs. Hill selected outstanding cultivars, many of which have been released into the nursery trade. This mountain-ash cultivar was selected from among seedlings grown at Longwood. It is remarkable because of its heat tolerance. It is one of the few Sorbus that does well in the humid summers of Southeastern Pennsylvania. The name of this cultivar refers to its spectacular fall color.

Wisteria frutescens 'Longwood Purple’

This wisteria, obtained by founder Pierre S. du Pont,  grew near the entrance to Longwood's Conservatory for many years. Mr. du Pont planted many wisterias and it is speculated that this was his favorite, as it is one of the few remaining in the Gardens today. The 5"-long pendulous flowers are a deep purple color and bloom in summer to early fall. This plant was selected because it has flowers that are darker purple than typical for the species. It has been distributed to nurseries and is commercially available.

Victoria ‘Longwood Hybrid’

The Victoria water-platters, named for the British queen, are native to South America. Victoria amazonica is found in the Amazon River and Victoria cruziana grows in the Parana River and other cooler rivers further south. In 1960, Patrick Nutt, in charge of Longwood's aquatic display at that time, made crosses between the two water-platter species. The final selection showed extreme hybrid vigor, with leaves growing to 5’ or 6’ in diameter. It also had darker green leaves, higher leaf margins, larger and more numerous flowers, and it was as hardy as V. cruziana, the hardier of the two parents. This cultivar is not available commercially, but can be found on display at botanical gardens around the world, including in England, Japan, and the United States.

Aesculus x dupontii

This buckeye was named by Professor Charles Sprague Sargent, Director of the Arnold Arboretum in Boston (from 1873 to 1927). He was a close friend of Colonel Henry Algernon du Pont and the Colonel's children Henry Francis du Pont and Louise du Pont Crowninshield. In 1924 in the Journal of the Arnold Arboretum, Sargent wrote: "This buckeye, which is one of the most interesting of the trees which have been planted in the United States, may well preserve among lovers of trees the name of a family which in at least four generations has made the neighborhood in Wilmington, Delaware, one of the chief centers of horticulture in the United States." The tree Sargent described was planted near the entrance to Eleutherean Mills (now the Hagley Museum and Library) after 1820 by Eleuthère Irénée du Pont de Nemours. The tree growing at Longwood, north of the Open Air Theater, most likely came from one of the seeds from the tree at Eleutherean Mills. This Aesculus grows to approximately 90’ tall and blooms yellowish-red in the middle of May. It distinguishes itself from other buckeyes by its good foliage retention in late summer.

Buxus sempervirens ‘Belleville’

Boxwood is an important element in Victorian garden design. From the beginning, Longwood has selected excellent boxwood specimens for the Gardens and for distribution into the nursery trade. The search for new and better boxwood continues as plants are collected and obtained from around the world. Mrs. Erwin W. Seibert obtained Buxus sempervirens ‘Belleville’ from Mr. Nick Bassler, a nurseryman near Belleville, Illinois, in 1931; her son, Dr. Russell J. Seibert, named it and brought it to Longwood during his tenure as the Gardens' first director.  The original plant at Belleville was growing one-half mile south of Scott Air Force Base. Selected for its cold tolerance, this Buxus is known for its dense, globular shape, and rich green-colored foliage. This boxwood is used in hedges in several places in Longwood Gardens including the Idea Garden and near the Open Air Theater. This plant was distributed to nurseries in 1964 and is commercially available.

Camellia x williamsii ‘Aida’

Pierre S. du Pont, Longwood’s founder, had an interest in camellias and started collecting them in 1912. He collected from many places, including importing them from France in 1916. They became a major component of the Conservatory and remain an important element of the present display. The camellia breeding project began at Longwood in the 1960s. Its main objective was to develop camellias that are reliably hardy outdoors in southeastern Pennsylvania. Dr. Clifford Parks, then with Los Angeles County Arboretum, in collaboration with Longwood Gardens, made the first crosses for the project in 1961. The plants were trialed at Longwood Gardens in an open plot in the nursery. Many were eliminated due to winter injury. ‘Aida’ was the only camellia trialed in the 1970s that survived two harsh winters, where the temperatures were close to 0ºF. ‘Aida’ originated from a seedling of a cross between C. japonica 'Ville de Nantes' and C. saluenensis 'Dogrose' and was received from Dr. Clifford Parks around 1968. Dr. Robert Armstrong, Longwood’s Geneticist, made the selection in 1974. The camellia breeding project continues at Longwood today. Although Camellia x williamsii ‘Aida’ cannot be seen on display, many other camellias are grown in the East Conservatory.

Hypericum frondosum ‘Sunburst'

Researchers at Cornell University, in Ithaca, NY, had been working on artificially induced tetraploid plants for many years. They induced tetraploidy in Hypericum in the late 1930s or 1940s. Dr. Richard Lighty, Longwood’s Geneticist in the 1960s, worked on this project as a graduate student at Cornell. The release of Hypericum ‘Sunburst’ was a joint project of Dr. Richard Lighty of Longwood Gardens and Dr. Robert Plaisted, Head of the Department of Plant Breeding at Cornell University. It was introduced and distributed by Longwood Gardens in the 1960s. This plant has been commercially available since then and has recently gained broad popularity.

Mandevilla ‘Alice du Pont’

Obtained from the Mitchel Estate in Oyster Bay, NY, in the mid 1930s, this plant was originally grown at Longwood Gardens as Dipladenia x amoena. In the mid 1950s, Dr. Donald Huttleston, Longwood’s Taxonomist, determined that this name might be incorrect. He sent samples to Dr. Robert E. Woodson, Jr., at the Missouri Botanic Garden in St. Louis for examination. Dr. Woodson identified the plant as Mandevilla splendens. Dr. Huttleston noticed that there was variation in the flowers of seedlings. In 1960, he studied some seedlings and found that they showed hybrid characteristics. Dr. Huttleston named this Mandevilla hybrid ‘Alice du Pont’ in honor of the wife of the creator of Longwood Gardens. This vibrant pink-flowered vine can be found throughout the Gardens in summer.