Orchids – amazingly evolved plants that have long fascinated botanists and the public. Their colourful and often intoxicatingly aromatic blooms, their symbiotic relationships with soil fungi and insect pollinators, their exotic nature and in some cases their rarity – orchids are among the world’s most popular, mysterious and engaging plants.

It’s often the case that an orchid is discovered doing what you least expect it to, only this time the result isn’t fascination and excitement, it’s deep environmental concern. There are a surprising number of orchids that have become invasive weeds around the world and the South African Weed Orchid (Disa bracteata) is one.

The South African Weed Orchid, aka SAWO, has become a highly invasive weed in several Australian states and is now marching across Victoria. It is primarily known from the west and central areas of Victoria, with a few records emerging in and around the Strathbogie Ranges – Seymour, Whiteheads Creek, Gobur and the Strathbogie Tableland. [see Afterword, at the end of this post]

South African Weed Orchid (Disa bracteata) distribution in Victoria (Map: Atlas of Living Australia). Arrows indicate the records from: the Burge Family Reserve at Gobur (1), Toorour (2) and Boho South (3).

In flower, this species is quite distinctive and seen close-up it doesn’t resemble any other Victorian orchid. The rosette of leaves at the plant’s base is distinctive. At a distance though, it can be confused with native species, such as the Common Onion Orchid (Microtis unifolia).

  • Common Onion Orchid (Microtis unifolia)
  • Common Onion Orchid (Microtis unifolia)
  • Sun orchid (Thelymitra pauciflora?)
  • South African Weed Orchid (Disa bracteata)
  • South African Weed Orchid (Disa bracteata) and Common Onion Orchid (Microtis unifolia)

Trust for Nature manages a variety of conservation reserves across Victoria and one of them, the Burge Family Reserve, sits on the edge of the Strathbogie Ranges at Gobur, just north of Yarck. Over the last few years, SAWO has been found at several places on the reserve and on an adjacent property. This year the reserve Committee of Management organized several working bees to better survey the reserve for SAWO, to map it’s distribution and remove as many plants as possible. As this year is a bumper year for native grasslands, finding an removing as many SAWO plants as possible, before they set seed, was a high priority. The working bees located, dug up and disposed of over 200 individual SAWO plants from several localities in the reserve. Subsequent work by a weed control contractor poisoned several hundred more plants. Neighbours Susan and Jonathon Hayman also diligently removed many hundreds of SAWOs from their conservation covenant, Billy Goat Hill.

The location of SAWO on the Burge reserve was GPS recorded and some of the locations were marked with stakes for follow-up management next season. As the records from Burge Reserve and from Toorour and Boho South, all documented this season, appear to be the most north-easterly Victorian records in the ALA, it’s important to warn land managers to be on the lookout – reducing the rate of spread and the ecological impact of this new weed is important.

Our work was aided by resources from:

  • Burge Family Reserve native grassland
  • SAWO in flower
  • SAWO with developing seed pods
  • Josh Graf & Ellen Purcell removing SAWO, Burge Family Reserve
  • Digging out SAWO
  • Lifting SAWO
  • Some of the SAWOs removed from Burge Family Reserve
  • Tubers, roots & leaves, SAWO
  • Halved tuber, SAWO

The Burge Family Reserve and neighbouring Billy Goat Hill property contain some of the best examples of native grassland and grassy woodland in the district. Burge Family Reserve has a Committee of Management that works with Trust for Nature to improve the vegetation and habitat condition for the many native species that occur there, including threatened species such as Plump Swamp Wallaby Grass (Amphibromus pithogastrus), Striped Legless Lizard (Delma impar) and Bibron’s Toadlet (Pseudophryne bibroni). More on these threatened species in another post, but for now here are some of this season’s images of the reserve.

  • Stunning cloud formations over Yarck Flora Reserve
  • Flourishing Kangaroo Grass (Themeda triandra) native grassland on Burge Reserve.
  • Scaly Buttons (Leptorhynchos squamatus) & Raspwort (Gonocarpus tetragynus)
  • grass
  • Swamp Wallaby Grass (Amphibromus sp.)
  • Rock chute controlling erosion at Burge Reserve
  • Fairies Aprons (Utricularia dichotoma)
  • Fairies Aprons (Utricularia dichotoma)
  • Old growth Yellow Box
  • Yellow Rush Lily (Tricoryne elatior)
  • Common Onion Orchid (Microtis unifolia)
  • South African Weed Orchid (Disa bracteata)
  • Spear grass (Austrostipa sp.)
  • Josh Graf & Ellen Purcell at a grazing exclusion plot, Burge Family Reserve

For more information about Trust for Nature or the Burge Family Reserve, contact Amelia Houghton, TfN’s North East Area Manager: ameliah@tfn.org.au or 0477 299 848

Afterword

After publishing this story, we’ve heard from several landholders in the Strathbogie Ranges that have seen SAWO on/near their properties: Fernhills Rd, Shean’s Creek and Weibye Track, Ruffy (28.11.2020).

Nick from Tree Headquarters, who treated much of the infestation on Billy Goat Hill and also in the Burge Reserve, comments ‘Properties around Seymour, Broadford and Strath Creek all have infestations of the weed orchid. A few plants found at the Cherry Tree Range wind farm, Seymour. Many thousands seen throughout Greens Pinch Reserve, Kilmore and they have taken over a property at Clonbinane.’ This is very depressing news and does suggest that the SAWO is already firmly established in the lower north east and it’s only a matter of time before it spreads even further (17/12/2020).