HIBISCUS
Queen of the Flowers
CHAPTER TWO

The Genetic History of Hibiscus rosa-sinensis

By Ross H. Gast
(Research Associate, Los Angeles State & County Arboretum, Arcadia, California)

Literature on the genetic history of ornamental hibiscus, commonly called Hibiscus rosa-sinensis, is very limited. Many factors contributing to its present state of development are not known; some have no doubt been lost forever. This paper has been prepared for the purpose of bringing together such facts as are available in print, supplemented by observations made in growing and hybridizing old forms and species during the past two decades. It is not offered as a definitive treatment of the genus, but an attempt to present background information for the hundreds of fellow fanciers and hybridises in many countries who are now showing serious interest in this group.

When referring to ornamental hibiscus as H. rosa-sinensis, modern taxonomists cite as their authority Linnaeus' Species Plantarum (1753). The type he referred to was probably the double red which had wide distribution throughout China, India, South-East Asia and the Pacific Islands in pre-European discovery days; later, a single red form was included in the taxonomic treatment of this hibiscus. In the early decades of the nineteenth century, other forms were introduced into the greenhouses of Europe as H. rosa-sinensis. Most of these were from Asia and the islands of the South Indian Ocean, where they were believed to have been grown before recorded history. Others were cultivars from interspecific crosses made by early plantsmen, in several parts of the world.

An outstanding contribution to the advancement of ornamental hibiscus development during this period was made by Charles Telfair (1), a dedicated plant lover residing on Mauritius, one of the Mascarene group. As early as 1820 he began crossing the native H. liliiflorus with old forms of H. rosa-sinensis brought to this tiny South Indian Ocean island, and sent propagating material of his hybrids to the famous plantsman, Robert Barclay, of Bury Hill, Surrey, who introduced them to English gardeners.

But the most significant and rewarding interest in bringing hibiscus species and hybrids together began about 1900 in Hawaii, India, Ceylon, Fiji and Florida, the centres of primary interest today. This work has clearly indicated that the ornamental hibiscus designated as H. rosa-sinensis is in reality a highly polymorphic group composed of complex hybrids and their derivatives. While its hybrid origin and the subsequent range of colour and form which may be produced from one cross heighten the interest in hybridizing as a garden hobby, it also suggests to the taxonomist that it should now be referred to as Hibiscus x rosa-sinensis to represent properly its hybrid nature.

Geographical Origin of H. rosa-sinensis

The literature on H. rosa-sinensis does not establish its geographical origin; however, most early references call it a native of China. As early as 1810, John Reeves, a tea merchant in China and collaborator-member of the Royal Horticultural Society, London, commissioned a Chinese artist to paint in water colours the various forms of hibiscus then grown in China, forms which he and others sent to England for propagation. Now in the Lindley Library of the Society, these illustrations include double forms of red, pink, buff, orange, yellow, and white hibiscus. No single forms of H. rosa-sinensis appeared in the collection, singles were considered rare in China, according to contemporary literature, and it was not until the introduction of the South Indian Ocean species a few years later that they became popular with English fanciers. Although H. rosa-sinensis was known and grown very early in China, and called 'Chinese Rose', Hu (2) says that "long accredited as a native of China, the wild form has not been discovered (in China)".

In India, H. rosa-sinensis was called Sehem-pariti, and later "shoe flower" by the Portuguese, who found it being used as a shoe polish by the natives, and a double red hibiscus was illustrated and described by Van Rheede (3) in 1678. The single red form was reported growing wild on the Malabar Coast of India, but this area has not been established as its native habitat. Such claims probably refer to H. rosa-malabarica (4) not considered allied to H. rosa-sinensis. Philip Miller, Curator of the Chelsea Physic Garden, London, introduced the double red and other forms of H. rosa-sinensis in England as early as 1731 under the name of H. javanica, calling them natives of Java. Cook and other Pacific explorers found the double red form cultivated in several island groups. Of its presence there the great Pacific-area botanist E. D. Merrill says, "(H. rosa-sinensis) is a pre-Magellan, man-introduced ornamental species from the West" (5), meaning of course, that it had been brought in to the Pacific during the Polynesian migrations from South-East Asia. This form is still commonly grown in all parts of the world where hibiscus thrives.

Hochreutiner (6), who places H. rosa-sinensis within Section Lilibiscus of the genus Hibiscus, offers the suggestion that this section "had its centre in the hypothetic Lemuria". Lemuria is said to be an ancient, sunken continent of which the Malagasy claim only Madagascar remains emergent. More convincing support of Hochreutiner's theory can be found in the fact that three - and possibly four - of the known species determined genetically compatible with all forms of H. rosa-sinensis and with one another, are native to the South Indian Ocean islands and the African East Coast, while no species with these genetic characters have been established authoritatively as endemic in Asia or the East lndies. The people of South-East Asia, favoured by seasonal winds, did migrate westward in the South Indian Ocean area, just as their brothers moved eastward into the Pacific during the great Polynesian migrations. Plant introductions could have moved either east or west; however, since most of the known compatible species were found in the South Indian Ocean islands and the African East Coast, these areas are the likely ancestral home of the early forms involved in the H. rosasinensis complex. The trade routes, of course, have had a great influence on plant distribution. In the case of hibiscus, it should be recorded here that following the discovery of the passage around the Cape of Good Hope by Vasco de Gama in 1497 and the subsequent establishment of Portuguese and Spanish trading centres in India and other Asian countries, the Mascarene islands, Madagascar and the African East Coast were colonized and became regular ports of call. In the Atlantic, the Canary Islands and Madeira were also favoured by returning trading vessels on the Cape of Good Hope route, and in 1798 Spain established the Orotava Botanic Garden on the island of Tenerife as an acclimatizing station for plants from Asia and the tropics. Thus, some of the oldest forms of H. rosa-sinensis may be found there.

The Genetically Compatible Species

The known species genetically compatible with all forms of H. rosasinensis and with one another are H. schizopetalus, an African East Coast species; H. liliiflorus from Mauritius and Rodriguey Island; H. fragilis and H. boryanus from Reunion Island; H. arnottianus and H. kokio (several forms of both) from Hawaii; H. storckii from Fiji, and H. denisonii, origin unknown. Most authorities agree that from these species - and perhaps some undetermined additional species - all forms of H. rosa-sinensis have evolved. It is quite possible, too, that among the many forms of hibiscus currently considered under H. rosa-sinensis there may be some that are, in fact, true species separable from this complex when it is understood more fully.

A comprehensive project having as its objective the development of hardier ornamental hibiscus cultivars was brought to Los Angeles State & County Arboretum in 1958 by the writer, who has been collecting and hybridizing both the older forms and the species of this genus for many years. Each season, these old forms, the several species, and their derivatives serve as parents of 2,000-3,000 seedlings produced for observation and additional breeding. During the past three years, the original collection has been increased by personal collections in Mauritius, Madagascar, East Africa, Singapore, Tenerife, Fiji and India.

Results of breeding work at Arcadia indicate that the geographical range of ornamental hibiscus can be greatly extended by selection of climatically "tailored" cultivars. It has been observed, for instance, that frost losses are minimized when cultivars with strong root systems resistant to low soil temperatures and excess soil moisture are planted. Efforts have been directed primarily towards the production of cultivars with this character. Selection of parent plants for this programme has been influenced to a large extent by the recorded "on the spot" observations of the author of forms of H. rosa-sinensis found growing in parts of the world considered marginal for ornamental hibiscus. Most of these forms have clear morphological evidence of their genetic origin, and with all of the species now available that are known to be cross-compatible, it is possible to select parents which will produce these hardier cultivars in many forms and colours.

LITERATURE CITED

1. Curtis' Botanical Magazine (1829), 56, t. 2891.
2. Hu, Shiu-Ying (1955). Flora of China, p, 47.
3. Van Rheede, H. (1678). Hortus lndicus Malabaricus, 2, 25, t. 17.
4. Edwards Botanical Register (1818), 4, t. 447.
5. Merrill, E.W. (1954). Botany of Cook's Voyage. Chronica Botanica, 14(6), 342.
6. Hochreutiner, B.P.G. (1900). Revision du genre Hibiscus. Ann Cons, Jardin Bot. Geneve, 4(1), 23-55.

The above genetic history is a reprint from Vol. XCLL, Part 8, Journal of the Royal Horticultural Society, August 1967 edition. Mr. Gast is an honorary member of the American Hibiscus Society and has many fine hybrids to his credit. Reprinted with permission of the Royal Horticultural Society, London and the author. Reprinted in Australia with kind permission of the Royal Horticultural Society, London, England, and the author.