Hibiscus & Malvaceae: Hibiscus insularisHibiscus malvaceae

• Hibiscus and other Malvaceae •

CULTIVATION • CONSERVATION • EDUCATION

Hibiscus and other Malvaceae: The genus Hibiscus is part of the Malvaceae, a taxonomic family that comprises thousands of species. Some members of this family possess considerable economic value, such as some Gossypium species (Cotton), while others are used as food sources, such as Abelmoschus esculentus (Okra), and Hibiscus sabdariffa (Roselle), used in jams and teas. Some species are used as fiber sources for jute and rope making, like Hibiscus cannabinus (Kenaf), and various Corchorus species (Jute). From times past (but perhaps to a lesser degree now), others supplied durable timber for woodworking, like some Talipariti and Thespesia species, and Hibiscus campylosiphon, an impressive tree from the Philippines.

Despite the undeniable value of the above-mentioned species, the worldwide fascination with the Malvaceae is credited to the unparalleled popularity of one of this family's most ornamental members, Hibiscus rosa-sinensis. Hibiscus rosa-sinensis cultivars are the result of crosses (both ancient and modern) between a limited number of species (from Lilibiscus ―a section of the genus Hibiscus containing about 10 species), the majority coming from the Mascarene Islands in the Indian Ocean and the Hawaiian Islands in the Pacific. This complex hybrid group was derived from a number of species that included most if not all of the following: Hibiscus arnottianus, Hibiscus boryanus, Hibiscus denisonii, Hibiscus fragilis, Hibiscus genevii, Hibiscus kokio, Hibiscus liliiflorus, Hibiscus schizopetalus, and Hibiscus storckii. Sadly, nearly all of these (as well as numerous other Malvaceae species) are now considered extinct or facing extinction in their natural habitats. For additional information on Hibiscus rosa-sinensis cultivars, go to the Hibiscus rosa-sinensis page.

The biological diversity (biodiversity) of our planet is rapidly decreasing in great part due to the direct and indirect consequences of human activity. Ironically, it is also through human activity and intervention that threatened and endangered species are offered their best chances for survival. Thankfully, in recent years, there has been increasing awareness regarding the profound importance of earth's biodiversity linked with the critically urgent necessity for human action to safeguard it. In the Biblical book of Genesis, we read "and the Lord God took the man and put him in the Garden of Eden to tend and guard and keep it", (Gen 2:15), conferring on humankind a role as Earth's primary caretaker. This 'tending, guarding and keeping' is best defined as having responsibility for the care and protection of the earth (stewardship), and affirms our commission for the wellbeing of this planet's vast community of life. Ultimately, stewardship of the earth, and conservation of its ecosystems is the responsibility of all people, not merely that of national governments.

The main strategies for conserving species are commonly referred to as ex situ conservation (out of the natural habitat) and in situ conservation (within the natural habitat). Ex situ conservation is accomplished through the efforts of botanical gardens, educational institutions, private gardens, and even seed banks. Although ex situ conservation is regarded as complementary to in situ conservation, in some situations it is the only option, ―the last resort when in situ conservation is no longer possible due to habitat loss and destruction. Some of the plants presented on these pages have suffered that fate and are currently classified as extinct, threatened or endangered in their natural habitats. In order to ensure their continued survival, an applied approach of 'cultivation, conservation and education' must be promoted. It is for this purpose that the entries found on this site are offered. Your feedback is greatly appreciated, especially in regard to errors.

Concerning the Historical References listed throughout these pages, please keep in mind that portions of the infomation presented may be outdated or incorrect. In addition, any dietary or medical information should be regarded as anecdotal. These references are included simply because they offer a glimpse of the horticultural history that is attached to many of these extraordinary plants. ―GB

Friday, December 18, 2009

Hibiscus insularis

Hibiscus insularis | Phillip Island Hibiscus

Hibiscus insularis is endemic to Phillip Island in the Norfolk Island Group, where the species is confined to three patches on the northern slopes (Green 1994; Mosley 2001). These plants have survived despite the grazing pigs, goats and rabbits which destroyed most of the Island's vegetation. With all of the introduced animals now removed from Phillip Island, seedlings are now growing near the original bushes. Hibiscus insularis was down to three or four bushes, and was in danger of extinction until cuttings were sent to the Sydney Botanical Gardens.

Although the species is listed as Critically Endangered (under the Australian Government's Environment Protection and Biodiversity Conservation Act 1999), it is now well established in cultivation. Hibiscus insularis is a dense bushy shrub to 4m. The 6-9cm blooms are produced freely in late summer and autumn. The flowers have cream colored petals which turn to a light purplish rose color with age. The crimson stigma pads are pronounced for a small flower. This Hibiscus is ideal for growing in coastal areas and is reasonably salt tolerant. Apparently, the plant retains a juvenile form for up to 10 years, with smaller leaves. Australian sources relay that it may take a number of years before the young plants reach maturity and they begin to bloom for the first time. For more information on Hibiscus insularis, see this excellent article: Hibiscus insularis

Historical Reference: Hibiscus insularis endemic on Phillip Island. A few plants still remain on the island, but those that I saw were in a most unhealthy condition, being covered with coccids, aphides, smuts, and other blights and pests. They were obviously maintaining an unequal struggle with an unfavourable environment.

   Transactions of the Royal Society of New Zealand
   Vol. XLVII, July 1915

Reference: It is not certain when rabbits were introduced to Philip but HOARE (1968) showed they were present in numbers in 1838. Today the vegetation is virtually absent. There are a few white oaks (Lagunaria) in the moister central valley, a straggly clump of Hibiscus insularis, and a few weeds, many of which are not native. A few scrawny rabbits remain. HOARE (1968) stated the pigs and goats were not exterminated until well into the third phase of settlement. One can surmise that the populations of these built up, possibly neglected in the early years of the third phase whilst the Pitcairners were settling in to their new home. Regeneration of shrubs would have been prevented and dry spells would have led to the goats reaching for the mature foliage of the scrub and the pigs grubbing for roots and gnawing at bark. Coupled with the island's natural tendency for soil erosion, these factors could have led to the gradual decline of the vegetation to a level where the larger herbivores might have died out naturally. Should the rabbits finally be exterminated, CUNNINGHAM'S notes provide a guide for efforts to restore the natural vegetation, though the Streblorrhiza and the topsoil are lost.

Philip now stands pinkly to the south of Norfolk, the pink relieved only by a few dark dots of vegetation. Numerous seabirds nest there and tourists come to marvel at the variety of hues of red, orange and yellow of the exposed subsoil. The fate of Philip Island should be borne in mind when considering the changes that have occurred and are still occurring on the main island.

   Series Entomologica
   Volume 13 of The Lepidoptera of Norfolk Island: Their Biogeography and Ecology
   Jeremy Daniel Holloway, Springer, 1966

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Friday, December 18, 2009

Hibiscus insularis

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