Trumpet vines are quite spectacular when in flower, from May to September in Pakistan. At the moment walls are ablaze with orange flower screens, and at first sight the trumpet-shaped flowers look a little like hibiscus, without the long stamen. These flowers attract honeybees and hummingbirds which feast on their nectar, stored deep inside the flowers, and so help pollinate the plants as the birds and bees get pollen on their heads and backs as they dive into the flower to reach the nectar. Trumpet vines are members of the Bignoniaceae family of plants and these are between 650 and 750 species around the worlds, with about 120 different genera.
The Chinese Trumpet Vine (Campsis grandiflora) has bigger flowers than other trumpet vines, as its Latin name suggests, and has been used in traditional Chinese medicine for a number of ailments for more than 2000 years. Extracts from the flowers and leaves have been subject to clinical trials and has been found to have antioxidative effects and this may not have come as a surprise to researchers as in traditional medicine it has been used to stimulate blood circulation and to cure diseases caused by sluggish circulation. The flower extract also has an anti-inflammatory action on the skin. Triterpenoids from the flowers may be beneficial in treating diabetes and they may also have cholesterol–lowering effects.
There is a blue trumpet vine in the Indian subcontinent, although the flowers are not so obviously trumpet-shaped. This one is Thunbergia laurifolia, which, as a non-native species is considered an invasive pest in north and south-east Queensland, Australia, where it is invading the rainforest.
Trumpet vines grow naturally in sub-tropical zones around the world, and the Campsis radicans is native to the Americas; it has yellow, orange or red flowers, and can grow to a height of 30 feet if it has a tall enough host to climb on. Normally trumpet vines are pruned so that they cover a wide area rather than growing tall. If they don’t have a wall or trellis or tree to climb, they will look like low shrubs. It has aerial rootlets which cling to the plant or structure it is climbing on, rather like Common or English ivy. It is sometimes called “Cow Itch” as both animals and humans can get dermatitis from it if the skin comes into contact with the leaves, in the same way as with Poison ivy, or Yellow Sage (Lantana camara).
Cape honeysuckle is an African indigenous species and has orange blossoms. This is used in traditional medicine as a pain-killer and to cure insomnia.
Trumpet vines are pretty to look at, but they can cause irritation to the skin, and modern medical science has yet to prove them effective against any disease. However, it is possible that new drugs can be developed from them.