Strongylodon macrobotrys

Jade vine (Strongylodon macrobotrys) was discovered in 1841 on the jungled slopes of Mount Makiling, on the Philippines’ Luzon Island, by members of the United States Exploring Expedition led by U.S. Navy Lt. Charles Wilkes . One can only imagine how startling that apparition must have been, but we are left only with the description of the Harvard-based botanist Asa Gray, who had locked horns with Wilkes previously and elected not to join the voyage. As part of the task of describing the thousands of plants collected by the multi-ship expedition, which ranged from Honolulu to Antarctica and involved several violent skirmishes with the natives (Wilkes was court-martialed at the end of the expedition, but acquitted), Gray named the vine in 1854. Its species epithet macrobotrys means “large grape cluster”, referring to the fruit. The genus name derives from the Greek strongylos or “round”, and odon or “teeth”, referring to the rounded teeth of the calyx. A member of the bean family, Jade vine is bat-pollinated in the wild, thus it must be hand-pollinated in greenhouses to bear its fruit, which can grow to be melon-sized. This has been done over the years at the Royal Botanic Gardens at Kew Gardens in England, where seed conservation is an ongoing focus, especially in the face of loss of rainforest habitat.[6]

The pale green foliage consists of three leaflets.[4] The claw-shaped flowers are carried in pendent trusses or pseudoracemes of 75 or more flowers and can reach as much as 3 m long.[4] The turquoise flower color is similar to some forms of the minerals turquoise and jade, varying from blue-green to mint green. The short, oblong, fleshy seedpods are up to 15 cm long and contain up to 12 seeds.[4]

The plant grows beside streams in damp forests, or in ravines.[4] The inflorescences are only produced by mature vines. Each individual bloom resembles a stout-bodied butterfly with folded wings; they have evolved certain modifications to allow them to be pollinated by a species of bat that hangs upside down on the inflorescence to drink its nectar.[4] The flowers are also visited by a species of wasp, and are home to a species of butterfly.

There are several other species of Strongylodon, but the superficially similar red jade vine, Mucuna bennettii, is a species belonging to a different genus, Mucuna. It seems to be endemic to the Philippines and is usually found in forests. Propagation has always been difficult. It is considered an endangered species due to the destruction of its habitat and the decrease of its natural pollinators. There seems to be a method of marcotting through mature woody stems. It is best planted in ground near a water source, but not inundated. The vine entwines itself through the trunk and branches of trees and the leaves spread over the canopy. The flowers hang like clusters of grapes.

The characteristic flower coloration has been shown to be an example of copigmentation, a result of the presence of malvin (an anthocyanin) and saponarin (a flavone glucoside) in the ratio 1:9. Under the alkaline conditions (pH 7.9) found in the sap of the epidermal cells, this combination produced a pink pigmentation; the pH of the colorless inner floral tissue was found to be lower, at pH 5.6. Experiments showed that saponarin produced a strong yellow colouring in slightly alkaline conditions, resulting in the greenish tone of the flower.[3]

Strongylodon macrobotrys is not frost-tolerant; it needs a minimum temperature of 15 °C (59 °F).[2] It is prized in tropical and subtropical gardens for its showy flowers which are a highly unusual colour, unlike that of almost any other plant. It is usually grown over a pergola or other tall support to display the spectacular cascading flower trusses which are produced generously once the vine is mature (after 2 years or more, depending on pruning regime). Curiously, on a large plant, the pale-coloured blooms can be difficult to see in strong sunlight and could be overlooked if not for the fallen blooms below the vine. Fallen blooms change color as they dry out, from mint green to blue-green to purple.

In South Africa the jade vine is mainly restricted to the warm humid strip of coastal Natal but grows in a few frost-free spots inland.

In colder latitudes the plant must be grown in a large glasshouse or conservatory, such as the famous examples grown at Kew Gardens, Cambridge University Botanic Garden,[7] Eden Project[8][9] and The Living Rainforest[10] in the UK.[4] In cultivation the plant flowers in early spring.[8] In the USA a jade vine can be found at the Naples Botanical Garden, Longwood Gardens, Franklin Park Conservatory, The New York Botanical Garden, Wave Hill, Greater Des Moines Botanical Garden, White River Gardens, and Nicholas Conservatory and Gardens. In Florida, it is at the Fairchild Tropical Botanic Garden, the Gifford Arboretum at the University of Miami, as well as Mounts Botanical Garden. And in Hawaii at the Hawaii Tropical Botanical Garden in Hilo, Lyon Arboretum in Honolulu, and Glenn’s Flowers and Plants in Waimanalo.

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  Strongylodon macrobotrys photographed at Huntington Gardens (Los Angeles)
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  A single jade vine flower
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  Jade vine fruit

Wikimedia Commons has media related to Strongylodon macrobotrys.

• Strongylodon macrobotrys A. Gray - inflorescence, stamen, pistil, ovary Images - Flavon's Wild herb and Alpine plants