South African Weed Orchid 1: Identification (DPI Vic)

December, 2002 South African weed orchid: LC0273 Identification ISSN 1329-833X Compiled by Jill Fleming (Horsham)

This Landcare Note describes the identification of the eradication. The weed has potential to impact on native South African orchid, Disa bracteata (Monadenia understorey flora, especially rare and endangered plants. bracteata). There are five main infestation sites in Victoria; Black Range – Stawell, Lake Eppalock – Bendigo, Deans Marsh Common and scientific names – Otways, Rowsley Valley – Bacchus Marsh and the South African weed orchid, African weed orchid, South Lower Glenelg National Park, which are currently under a African orchid or Brown finger orchid. Disa bracteata control and monitoring program. The other known (Sw.) T.Durand & Schinz. Family Orchidaceae (orchids). infestations throughout the state have been contained and have long term monitoring programs in place. Status The weed is likely to be introduced accidentally on South African orchid is not a proclaimed species anywhere vehicles and machinery due to poor hygiene practices, in Australia. The weed is identified as a New and spread by seeds on clothing, shoes and camping Emerging weed in the Wimmera Weed Action Plan 2000- equipment, and by wind dispersal. 2005, with 1 ha currently infested in Wimmera Catchment The plant grows readily in competition with a wide range Management Authority region. It gained this status after of other flora including grasses, it invades bushland and being identified as a significant threat to environmental pastures and is attracted to disturbed sites. The South values and all known infestations in the Wimmera could African orchid, will grow in all light conditions and is not be treated within three years to achieve containment and/or fussy about soil types.

Figures 1. South African orchid, Figure 2. South African orchid infestation sites in Victoria. showing flowering and vegetative parts.

Background and distribution The largest family in the world, orchids represent nearly a tenth of all flowering plants. Orchids occupy a diverse range of habitats and are most diverse and abundant in the moist tropics. They are important ecologically having symbiotic relationships with soil fungi and most are dependent on specific insect pollinators. Unlike our threatened native orchids, D.bracteata is self-pollinated and each plant produces tens of thousands of airborne seeds. In its native South Africa, it grows in the Cape Province – home to many of our weeds, from sea level to 2000m. It was first noticed naturalised near Albany, Western Australia in 1944, where it now invades several thousand square kilometres. The 1990 records show it spreading as far north as Geraldton and east to the Israelite Bay. D.bracteata first appeared in South Australia in 1988, spreading rapidly in the 1990’s. It is believed to have escaped from orchid enthusiasts, where it was cultivated as a curiosity. In South Australia, the problem has at least doubled annually and the local spread has averaged some 10km/yr north and south. Current knowledge is that there Figure3. A flowering stem of South African orchid. are at least 10 ha infested in Victoria. The first recorded Seeds – black, minute and dust-like, contained within the infestation in Victoria was in the Rowsley Valley near capsular fruit. The species is autogamous (self-pollinating) Bacchus Marsh in 1991. Infestations in Victoria are also and thus produces a large amount of seed per plant. The likely to be the result of garden escapes. seeds may be blown many km and can remain viable for seven years. Seed set and dispersal starts at the end of Identification/Description November. The seeds continue to mature in the capsule if South African orchid is a deciduous perennial terrestrial the flower head is picked and the capsule shatters and orchid with underground tubers. Dormant for much of the disperses them when ripe. year, it sprouts in early spring and takes a minimum of Tubers – Generally thought to have 1–3 tubers, similar three years from seed to flowering stage. shape to a garlic clove or bulbs, about 20mm in size. The Stems – Erect and fleshy usually 30 – 50cm tall. plant also has a mass of fleshy side roots and there is no Leaves – Leaves numerous with parallel veins, decreasing main tap root. in size progressively up the stem; lower leaves 5-15cm long, tapering from a broad base to an acuminate apex. Flowers – from late October through to December in Victoria. 15-30 on a thick cylindrical spike 5-20cm long, which resembles a greenish-brown asparagus spear. Flowers very dense, arranged in an indistinct spiral, mostly reddish-brown and yellow with a leafy bract.

Figure 4. Tubers and vegetative parts of South African orchid. If uncertain about the identification consult the keys to the Orchidaceae in the Flora of Victoria (Volumes 2 and 4) or submit specimens to the Herbarium of Victoria.

Further information Marchant, N.G. Wheeler, J.R. et al (1987) Flora of the Perth region, vol 2, Western Australian Herbarium, Department of See the Landcare Note: South African weed orchid – Agriculture, Perth, WA. management, for a information relating to the control Walsh, N.G and Entwisle, T.J. (1994, 1999) Flora of Victoria and management of this plant. Volumes 2 and 4. Melbourne, Inkata Press. For further technical advice please contact a Catchment Acknowledgments Management Officer at your Department of Sustainability and Environment office. Prepared by Jill Fleming with the kind assistance of Ian Faithfull (Keith Turnbull Research Institute), Stuart References Lardner (DSE Horsham), Mark Farrer and Celeste Ellice Backhouse, G. (2000) The occurrence of the South African (DSE Stawell), Kate Blood (Weeds Cooperative Research orchid Disa bracteata Sw. in Victoria. Austral. Orchid Review Centre). Photographs by David Venn (DSE Horsham). 65(5), 22. Find more information about DSE on the internet at Jessop, J.P and Toelken, H.R, (1986) Flora of South Australia http://www.nre.vic.gov.au/ or call the DSE Customer Part IV. Adelaide, South Australian Government Printer. Service Centre on 136 186.

This publication may be of assistance to you but the State of Victoria and its employees do not guarantee that the publication is without flaw of any kind or is wholly appropriate for your particular purposes and therefore disclaims all liability for any error, loss or other consequence which may arise from you relying on any information in this publication.