Botanical Name: Dodonaea viscosa
Dodonaea viscosa, commonly called ‘sticky hop bush’, is a member of the Sapindaceae family. This genus of plants are known as hop bushes and they were used to make beer by early European Australians. Dodonaea viscosa has also been traditionally used by Aboriginal Australians to treat toothache, cuts and stingray stings.
Dodonaea viscosa distribution
Dodonaea viscosa can be found in every state and territory of Australia. However it is highly variable and consequently has seven sub-species recognised. The seven sub-species of Dodonaea viscosa are D.viscosa subsp. angustifolia, D.viscosa subsp. angustissima, D.viscosa subsp. burmanniana, D.viscosa subsp. cuneata, D.viscosa subsp. mucronata, D.viscosa subsp. spatulata and D.viscosa subsp. viscosa. These sub-species each have a distinct habitat and can handle varying degrees of drought. The major differences of the sub-species are in distribution, form and leaf characteristics. It is best to plant the sub-species found in the local area; this species will have adapted to these particular environmental conditions.
In general, Dodonaea viscosa is an extremely hardy species and is able to resprout from the base. The stand-out horticultural feature of this species is the brilliant colour of the capsules. Other desirable features include its successful use as a hedge due to the dense habit. There is also a popular non-native form with purple foliage, referred to as Dodonaea ‘Purpurea’.
Dodonaea viscosa flowers are inconspicuous, with no petals. These flowers occur during spring and summer and are less than a centimetre in size. The plants are dioecious; i.e. the flowers are male or female and usually occur on separate plants.
Hop bushes have important cultural and medicinal roles
Aborigines and colonists alike had a great affinity for hop bushes, which prove to be true ‘people plants’ due to their cultural significance and medicinal properties. Known as ‘oyster bush’ by aboriginal tribes, their conspicuous orange/red winged seed capsules acted as a seasonal indicator which heralded the most opportune time to collect the bounty of succulent oysters from the nearby rocky estuarine foreshores. The colonists, impressed by the similarity in looks and taste the seed capsules had to hops, successfully brewed a tangy, bitter but acceptable beer alternative.
Recent pharmacological analyses of hop bushes reveals the presence of a rich set of active alkaloids, tannins, flavonoids, organic acids and 1-8 cineole rich oils. The relative concentrations of these ingredients vary widely depending on the environmental conditions and habitats where they occur. This variation in relative potency of active ingredients is also subject to seasonal differences at the time of harvest. Although the hop bushes are found in many distant countries, it is uncanny how unrelated local indigenous populations attributed similar cultural and medicinal uses to this ubiquitous plant.
Cultural uses by Aboriginal populations
Common amongst older aborigines were the persistent problems of toothache as a result of decades of grinding highly fibrous diets. By chewing the leaves of the oyster bush, mild analgesic and euphoric effects provided relief from nagging toothache. Aboriginals used the term ‘Pitori’ for plants such as hop bushes that acted as painkillers.
Inflammations from rashes and bruises as well as jelly fish and stonefish stings were eased by binding wads of chewed leaf pulp on the affected areas. The bitter juice exuded from the leaves during the preparation of these wads was not swallowed but collected as an antiseptic. The leaves were known to reduce inflammation and swelling as well as imparting an antimicrobial protection to open wounds and infections. The Central Australian Aborigines (like indigenous Indian tribes) were reported to rely on the leafy branches as a customary means for relief of flu-like fever and body aches. The leafy branches were smoked on warm ash beds releasing 1-8 cineole rich oils (well known active ingredient in the essential oils extracted from Gum (Eucalyptus sp.), Tea Tree Leptospermum sp., Paperbarks Melaleuca sp. and native mint bush Prostanthera sppThe smoke would act as a febrifuge (fever reducing agent) by reducing the swelling of mucous membranes and loosening phlegm thus freeing the airways.
Also common amongst colonists and aboriginals were digestion and elimination problems. This was a result of hot weather, poor food hygiene and sub-standard nutrition. Australian aboriginals, like indigenous people from North America, Mexico and South Africa, used the tannins (dried stems/leaves contain 14% tannin) and flavonoids properties of the hop bush by applying poultices of fresh leaves to relieve diarrhoea, stomach and uterine cramps. The typical mode of action (as reported in pharmacological studies) acts to sedate smooth muscle contractions.
The Aborigines of south eastern Australian preferred to construct their temporary shelters from D. viscosa var. angustissima simply because the dead branches retained their leaves.
It has been recorded that the South America Peruvian Indians developed a culturally accepted practise of chewing the hop bush leaves in the knowledge that it acted as a substitute for Coca Erythroxylum coca. Like betel nut, the younger viscous (sticky) leaves were often chewed with ash, lime or magnesia to neutralise the organic acids binding the active ingredients, thus enhancing its stimulant and euphoric effects. Of course, akin to betel nut chewers, the lime would have caused rapid tooth decay.