Strongylodon macrobotrys (jade vine)

Restricted to the rainforests of the Philippines (Luzon, Mindoro and Catanduanes Islands).

Strongylodon macrobotrys (Image: Brian Schrire)

The jade vine is a woody vine with stems which can grow up to 18 m long. The leaves have three leaflets and are up to 25 cm long. The flowers are in pendent trusses (pseudoracemes) up to 3 m long, comprising many luminous blue-green flowers measuring up to 6 cm across. The flowers show modifications associated with pollination by bats. The shortly oblong or rounded fleshy pods are up to 15 cm long, quite unlike the typical legume pod, and contain up to 12 seeds.

The rainforests of the Philippines are disappearing at an alarming rate – originally the islands were almost completely forested, but a 1988 survey estimated that only 20 per cent of the forest remained. The speed at which the rainforest is vanishing adds a sense of urgency to Kew's research into the jade vine’s floral biology.

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Strongylodon macrobotrys vine (Image: Phillip Cribb)

Though the jade vine is a rare sight in the wild, British botanic gardens have had great success in growing it. It flowers happily here at Kew, at Cambridge and also at the Eden Project in Cornwall. However it is one thing to get the plant to flower, and quite another to get it pollinated so that the huge bean-like pods will develop to contain fertile seeds.

In the wild the jade vine is pollinated by bats, so when the plant is cultivated in a hothouse the horticulturalists in charge of it, using their hands, have to mimic the effect of bats visiting the plant to drink nectar. The bats hang upside down to sample the jade vine’s nectar, and the plant gently brushes pollen onto the bat’s head while it drinks. The next plant the bat visits collects the pollen from the first before brushing its own pollen to be transported elsewhere. It is a great example of co-evolution in action; the plant and the bat have evolved to work perfectly in cooperation with each other.

In 1995, Chrissie Prychid at Kew used this technique to get the jade vine in the Palm House to make pods for the first time in over thirty years. The pods were so heavy they had to be supported with makeshift string nets to prevent them dropping off before they were ripe. Once we understand how to grow rare and endangered plants at Kew, it allows us to develop new techniques and expertise which can be passed on to local conservationists in our partner countries, so that in the future they can safeguard their own plant heritage.

The jade vine is cultivated as an ornamental plant.

Strongylodon macrobotrys vine (Image: Peter Gasson)

Jade vine has been successfully propagated from nodal cuttings at Kew. A small slice is made at the node at the end of the cutting to encourage callus development. A potting mixture containing 50% perlite is used initially, but the cuttings are then placed in richer compost after rooting has occurred. Bottom heat is provided and the cuttings are kept in a transparent plastic bag to prevent them from drying out. Rooting is easily achieved within six weeks. July is the best time to take cuttings at Kew, as the parent plant will have put on plenty of growth at that time. If several cuttings are to be taken from a long piece of stem, it is essential to mark the top and bottom of the stem to avoid confusion and ensure that the cuttings are placed the right way up in the compost.

After about 18 months, the new plants will have produced several metres of growth. They need to achieve plenty of vegetative growth in order to flower. It is thought that they should be kept under glass in humid conditions at around 20-30 °C, but Kew is experimenting with some plants in cooler, drier conditions.

Jade vine can be seen growing in the Palm House and the Princess of Wales Conservatory at Kew.

See the jade vine at Kew Gardens

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