Hop Bushes or more endearingly called "Dods" (Dodonaea viscosa spp.), provide an interesting brew of enthralling plant characteristics, uses and interrelationships. Their robustness enables them to flourish across a diverse range of open vegetation communities spanning areas of continental Africa, America, Australia and India. With its natural habitat spreading from exposed coastal fore dunes and cliffs, to barren rocky ridges and grassy woodlands communities, it has earned a reputation as a hardy, water miser. Combined with its plant uses and attractive, vividly coloured 3 to 4 winged fruits, glossy leaves and natural hedging ability, it deserves a recent increase in popularity as a desirable landscape and revegetation plant.

Subspecies of Dodonaea viscosa have distinctive characteristics

Dodonaea viscosa spp. has a series of subspecies occurring in open woodlands in SE Australia. Their plant size, distinctive leaf shape and habitat range helps to distinguish between them. Key examples include Dodonaea viscosa ssp viscosa (large, nearly stalkless, elliptical leaf), robust Dodonaea viscosa ssp spathulata, (spoon shaped leaf), the attractive Dodonaea viscosa ssp angustissima, (delicate linear leaves), the arid area Dodonaea viscosa ssp mucronata (pointy tipped spoon-shape leaves) and the appealing purple leafed screening or accent favourite from New Zealand Dodonaea viscosa ssp purpurea.

Recently variegated and a prostrate forms of Dodonaea viscosa ssp spathulata have proved very popular as landscape features and accent plants. All the above species form excellent water wise informal screens or formal hedges (biennial pruning necessary). Some of the most classic forms of these plants can be enjoyed in very exposed sites such as sea cliffs or frontal dunes where the wind shearing effect has resulted in unique and photogenic botanical marvels.

Hop Bushes are unusual members of the Soapberry family

There are 66 Dodonaea species, elevating it to being the largest genus of the 150 genera Soapberry family Sapindaceae, ("Sapo" Latin for soap). Many family members contain a saponin glycoside, which provides plants with a useful detergent-like foaming attribute acting to reduce the water tension when shaken under water. In contrast to open dry woodlands where Hop Bushes flourish, most of the family members are found in closed, tropical forests, being prized for their well known fruits. These include the luscious Lychee Litchi chinensis and Rambutan Nephaleum lappaceum along with the sticky sweet Asian delights from the Tamarind seed pods Tamarinus indica. All these tropical members attract the pollination services of a variety of insects and birds by boldly marketing their flowers with alluring nectaries, scents and colours. Their irresistible fruits ensure the forest fruit eaters disperse their seeds far and wide.

Dry, exposed woodland communities enhances their long term survival

In contrast to the families' main pollination process, the Hop Bush is surprisingly a wind pollinated plant. The Dodonaea floral structure, colour and lack of scent provide cryptic clues in this regard and help in understanding why it flourishes in dry, exposed vegetation communities. Missing from the flowers are the obvious bold coloured petals, sweet chalices of nectar or alluring scent essential for the tropical family members to advertise their rewards in exchange for insect or bird pollination services. Closer observation reveals that the flowers are at the ends of branches with their stigmas having a broad sticky collecting surface ideal for catching airborne pollen. With disproportionate numbers of anthers (relative to stigmas) they are capable of wafting clouds of fine yellow pollen into the breeze where they can travel some two kilometres during their pollination season. As obvious wind pollinated flowers they thrive in exposed, dry landscapes allowing the wind to do its job.

By establishing itself in prominent single species groves within low diversity, open plant assemblages, Hop Bushes, like other wind pollinated native trees and shrubs, such as She-oak (Allocasuarina verticillata) and North-Esk Pine (Callitris oblonga) improve their chances that the pollen will reach its target. Like Hop Bushes, these species are dioecious having male and female flowers on separate plants. It is also interesting to note their pollen transfer occurs when the warm dry breezy conditions of late spring to early summer arrive after the rainy, humid conditions have waned.

Hop Bushes enhance bird and insect diversity

Hop Bushes' three dimensional twiggy and leafy frameworks are an open invitation for the wheel webbing spiders to weave their intricate webs to capture unsuspecting passing insect prey. These webs are diligently collected for binding the fibrous grass strands during nest building by insect and seed feeding birds such as Brown Thornbills, Flame, Scarlet and Dusky Robins, Welcome Swallows, Strong-Billed and Black Headed Honey Eaters, Grey Fantails, Eastern Spine Bills and Dusky Wood Swallow. Other large seed eaters such as Bronze winged Pigeon, Beautiful Firetail (Tasmania's only native Finch), Musk Lorikeet and Green and Eastern Rosella devour the nutritious winged seed clusters before they are either feasted on by seed weevils or glide to ground. Mid-storey bushes like Hop Bush and Native Box (Bursaria spinosa) planted into the park style urban landscapes and gardens provide an important role in helping to attract these seed and insect eating birds at the expense of the aggressive domineering nectar feeders such as New Holland Honey Eaters, Noisy Minas and Wattle Birds.

Recommended Readings

• Whiting, J., etal., 2004. Tasmania's Natural Flora. Tasmania's Natural Flora Committee;
• Van Wyk, Ben-Erik, 2003. Gericke, N., People's Plants; A Guide to Useful Plants of Southern Africa. Briza Publications.
• The Collection Newsletter Volume 6, Issue 1, 2004. Dodonea viscosa Hop Bush www.tcbmed.com/newsletters/volume6-Issue1
• Closs, J Dodonea Study Group 1993 Dodonaea Australian Plants Journal 17/137
• Latz Peter, Bushfire and Bush Tucker, Aboriginal Plant use in