Dodonaea viscosa subsp. angustissima - Narrow-leaf Hopbush

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Dodonaea viscosa subsp. angustissima - Narrow-leaf Hopbush

Dodonaea viscosa and its 7 subspecies is extremely widespread, being found in all Australian States, NZ, PNG and islands in the Pacific and Indian Oceans. However subsp. angustissima is largely an inland species and is only found on the Australian mainland, where also common and widespread.

The seed of this plant germinates readily after fire or soil disturbance and has become a serious weed of pastoral areas of western NSW, although in the Esperance region it is not commonly encountered. Here it is mainly found on and around inland clay/gypsum saltlakes, where it exists in scattered small colonies, but elsewhere it is often found in much larger numbers and a variety of habitats.

The early settlers used the bitter hops for making beer, so it was probably introduced to areas where it did not naturally occur and due to its weedlike habit, soon became well established. The leaves are to some degree cyanogenic, so not readily eaten by stock, which meant it could also spread freely.

Dodonaea viscosa subsp. angustissima with its narrow leaves is very drought tolerant, which is another reason for its colonising ability in arid areas. However it is the leaf size and shape that largely determines the 7 subspecies, with generally the wider leaf forms occurring in wetter regions to make Dodonaea viscosa a highly variable and adaptable species.

In the Esperance region there is only one other subspecies that could be confused with subsp. angustissima and that is subsp. spatulata, which has leaves greater than 6 mm (1/4”) wide and are broader at the top than the bottom, plus they have a petiole (stalk). D. viscosa subsp. angustissima on the other hand has leaves that are less than 6 mm wide and mainly linear throughout, plus are sessile (without a petiole).

Locally D. viscosa subsp. angustissima can grow to 4-5 metres (15’) in height, but mostly they are around half that; the colourful hops are produced from October to December, but are likely to occur at almost anytime due to its extensive distribution and Australia’s variable climate.

There are all male and all female plants, with the male flowers having only a group of anthers that release pollen to the wind that by chance is carried to the females, although pollen collecting insects probably also play a part. Of the scattered colonies of this species, the composition of male and females plants is quite random, with some colonies being all male and others mostly female, which with their scattered distribution, probably stops it from becoming a weed as it does elsewhere.

Dodonaea is part of the Sapindaceae family.

Dodonaea lobulata - Bead Hopbush

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Dodonaea lobulata - Bead Hopbush

There are around 70 Dodonaea or Hopbush species worldwide, with over 60 spread throughout Australia and of which 59 are endemic. They grow in a variety of habitats although many prefer the more arid regions, so are well adapted to hot/dry conditions. The family Sapindaceae contains a number of useful species including the Tulipwood, Lychee and the Tamarinds, with a number of colourful Hopbush species grown for ornamental purposes.

Dodonaea lobulata is an inland species, growing to 3 metres (10’) in height and in WA mainly found within a 400 km (250 mile) radius of Kalgoorlie, although is also indigenous to SA and NSW. Around Esperance it can be common, but is largely localised to red-loams around low-lying granite outcrops, plus with a limestone substrate shallowly overlying the outer granite perimeter.

Locally, the habitat type above is not uncommon in the mallee zone to the northeast of Esperance, which typically has a fine grey sand/clay soil over limestone. This dry mallee environment surrounds the low-lying granite outcrops and drains from the limestone onto them, instead of the elevated outcrops, where the drainage flows from the granite to surrounding areas. Dodonaea lobulata in these habitats is usually within 20 metres of the exposed granite. Elsewhere it tends to occur on heavy loams in rocky and/or limestone regions.

The leaves of Dodonaea lobulata are slightly viscid (sticky) and give off an aroma that is likened to cinnamon or mixed spice; the shrub itself is named after the small lobes attached along both sides of the leaves. The fruits or hops (named after the similarity to brewing hops), are initially coloured a pale green/yellow, but quickly take on a red flush that deepens to scarlet as the fruit matures. The flowers are very small and insignificant and play a lesser role to identification than the fruit and foliage.

As these plants usually grow in dry areas with highly irregular rainfall, they are very opportunistic to favourable flowering conditions after good rainfall, so timing can vary considerably with hops appearing anytime during winter and spring, although once they do, they are held ornamentally in full colour for a number of weeks.