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Allamanda cathartica L. 1771
pronounced: al-luh-MAN-duh kath-AR-tick-uh
(Apocynaceae – the oleander family)
common names: Allamanda, Yellow Trumpet, Golden Cup
Allamanda is named for the Swiss botanist Dr Frédéric Allamanda (1735–1803); cathartica is from the Greek καθαρτικος (kathartikos), for cleansing or purifying, i.e. purgative (laxatives are made from the plant).
This woody, evergreen scrambling shrub or vigorous evergreen climber (var. hendersoni) is a relative newcomer to North Queensland. A native of South and Central America, it was listed in nursery catalogues in Victoria as early as 1855. It was first recorded as naturalized in North Queensland in 1945, although it had been grown in Brisbane Botanical Gardens in 1933. Being easily spread by wind and water, it has now become an invasive weed in many parts of North and Central Queensland. It is found growing wild in parts of Magnetic Island. The climbing variety is particularly invasive. There are some cultivated stands. Those outside Foodworks in Nelly Bay are looking very attractive as I write these notes. I think they are probably a dwarf cultivar.
The colourful cultivar ‘Cherry Ripe’ is also becoming popular on the island, and there are several plantings by the City Council Parks Department, especially near the public lavatories in both Nelly Bay and Picnic Bay. ‘Cherry Ripe’ will grow upright, but does better with some support from below for the branches. As an espaliered plant on a fence or trellis, ‘Cherry Ripe’ is superb. It also makes a spectacular display if grown on a pillar with strong supports. Most allamandas will climb or scramble if given the chance – it is indeed when they scramble in unwanted places that they become a pest. ‘Cherry Ripe’ will also do well in large decorator pots on a patio, balcony, or around a swimming pool. Wherever and however it is planted, like all allamandas it likes either full sun or very light shade; and also, in common with other allamandas, it is a gross feeder, and is best grown with heavy mulch. The plant, which has a persistent root base, needs annual pruning, which is best done in winter, when it will stand quite hard pruning.
The plant, which in its vine form can climb to about 4.5 m, and in its shrub form to about 2 m, has glossy deep green leaves that provide the perfect foil for the flamboyant flowers. The leathery leaves are lanceolate, and may be either opposite or in whorls of three or four. The flowers are a dramatic trumpet shape, up to about 12 cm long, with a widely flared throat and 5 large overlapping petals, usually golden yellow in colour.
Fruits are seen only rarely. The rounded fruit is covered in spines about 1 cm long. Allamandas prefer full sun, and in our climate flower prolifically, particularly after good early summer rain.
Care should be taken when pruning them, as they exude a milky sap that may cause skin irritation. All parts of the plant are toxic if ingested. Propagation is usually by cuttings in late spring.
In cooler climates allamandas are often grown in pots or in hanging baskets. There are cultivars in colours other than yellow: white, purple, pink or orange are the most common. These cultivars tend to have larger blooms, and seldom produce seeds. In the wild, allamandas grow in roadside ditches, along riverbanks and other open, sunny areas, in abandoned yards, and dumps. They do not like shade, or salty or alkaline soils. In appropriate conditions they can grow up to 3 m a year. As a controlling measure, cutting is ineffective and will lead to vigorous coppicing.
Allamanda cathartica is also notable for its medicinal properties. The leaves, roots and flowers may be used in the preparation of a powerful laxative, hence the name. The milky sap has some antibacterial and possibly anticarcinogenic properties, but, as mentioned above, in its raw state will often cause gardeners regularly exposed to it to develop rashes, itches and blisters.
Information about medicinal qualities of plants, or about their use as medicines, is for interest only, and is not intended to be used as a guide for the treatment of medical conditions.
Photographs taken 2008, 2010, Nelly Bay, 2018 Picnic Bay
Page last updated 11th September 2018