Australian Broomrape (the good one)
In 2020, we found a Broomrape. It was, annoyingly, growing in the middle of the track. It was dry and shriveled but somehow we had managed to avoid slashing it.
Broomrapes are a parasitic species but information about their host plants is scarce. They contain no chlorophyll of their own and only the flowering stem can be seen above ground for a few months each year. Australian native Broomrape (Orobanche cernua var. australiana) is very rare in Victoria, but Branched Broomrape (Orobanche ramosa) is a state-prohibited weed. Branched Broomrape and other weedy Broomrapes which “pose a serious threat to Australia’s broadleaf grain and vegetable industries”. So, I was a bit excited but nervous too, which one could it be …?
We hoped our shriveled specimen would be the good one. Neville Walsh, Senior Conservation Botanist at the Royal Botanic Gardens Victoria was hopeful too. His initial thoughts from the photographs were that it was the native Australian Broomrape. He said, “This (in my humble opinion) is a HUGE record … O. cernua var. australiana is a plant that I've been hoping to see but never have, and had harbored fears that it might be extinct in Victoria.”. Neville asked for a specimen to confirm…
Update Damn, damn, damn. Neville quickly confirmed, when he had the specimen in hand, that it was actually the weedy (but not particularly nasty) Orobanche minor.
One day, I hope to find the native Broomrape in the Mallee. My friend “Cinclosoma” reports “I located ten or so following a fire in about 1973, a little way south and west of the junction of the Murray Valley Highway and the Hattah Kulkyne National Park entrance. Later I chanced upon a few more, south of Barney’s Track, on a sandy ‘plateau’ south of the big Zig Zag Dune, again following a fire. At the time, I formed the opinion that the reproductive cycle of this plant was linked to the occurrence of fire, much after the fashion of the Azure Daisy-bush (Olearia rudis), which incidentally, were evident and in full flower at the time.”
Broomrape, on Raakajlim in 2013. This is probably the weedy Orobanche minor
Turns out, I’m not the only one who has misidentified Broomrapes. This is from the Summer 2020/21 Weed Spotter Newsletter: https://agriculture.vic.gov.au/support-and-resources/newsletters/weed-spotters
Broomrapes and how to identify them
Branched broomrape Orobanche ramosa is an unusual State prohibited weed because it is Victoria’s only declared parasitic plant. Parasitic plants do not photosynthesise and can only survive by extracting all their required nutrients and water through attaching to the roots of susceptible host plants. Branched broomrape parasitises a range of species in Australia from several plant families, including native plants, commercial species (crops and pasture plants) and weeds.
Branched broomrape is yet to be found in Victoria. However, there are two other species of broomrape that are known from Victoria: the native and rare Australian broomrape, O. cernua var. australiana and the introduced weed lesser broomrape (also known as clover or common broomrape), O. minor.
Branched broomrape is significant pest, with major crops being seriously affected when this species becomes established, hence its declaration as a State prohibited weed.
Agriculture Victoria received an above average number of broomrape reports during Spring 2020, all of which turned out to be O. minor. Some information on how to distinguish between the broomrape species is provided below.
First published 2 November 2020
More information:
South African Weed Orchid - http://www.viridans.com/INTRO/waitingweed.htm
Australian Broomrape - https://vicflora.rbg.vic.gov.au/flora/taxon/6f801dc5-3a3a-4520-8df6-3f3e40c7740f
Weedy Broomrapes - https://www.pir.sa.gov.au/__data/assets/pdf_file/0017/232433/Orobanche_spp_June_2011.pdf
Branched Broomrape in Victoria - https://agriculture.vic.gov.au/biosecurity/weeds/state-prohibited-weeds/branched-broomrape
Barker, W R 1999, ‘Orobanchaceae’ in N G Walsh & T J Entwisle (eds), Flora of Victoria Vol. 4, Cornaceae to Asteraceae, Inkata Press, Melbourne, viewed 02 December 2020, Australian broomrape and lesser broomrape.
Department of Primary Industries (DPI) 2003, ‘Weed Alert: Branched broomrape, Orobanche ramosa’, Under Control, Pest Plant and Animal Management News, no. 25, pp. 10-11.
Faithfull, I & McLaren, D 2001, Landcare Notes: Branched broomrape – identification (LC0272), Keith Turnbull Institute, Department of Sustainability and Environment, Frankston.