Sevenhill Nature Reserve contains the largest known population of the nationally Endangered orchid Caladenia argocalla (White Beauty Spider-orchid). This species is protected under the Commonwealth Environment Protection and Biodiversity Conservation Act 1999. It is currently known from thirteen populations, which mainly occur in the Clare Valley and the Barossa Valley regions of South Australia and has a total population size of 4,300 mature plants. Sevenhill nature reserve contains approximately 70 percent of the total population of Caladenia argocalla (approx. 3000 plus mature plants).
Caladenia argocalla (White Beauty Spider-orchid). Photo: Joe Quarmby
Caladenia argocalla typically grows in Eucalyptus leucoxylon (South Australian Blue Gum) grassy woodlands on gentle hill slopes, often with a southerly aspect. Soils are typically clay loams with high humus content in the surface layer.
Caladenia argocalla usually produces a leaf in July or August. However, it does not always produce a leaf or flower every year. During mid August to mid September Caladenia argocalla produces buds, followed by flowering in late September to late October. Underground tuberoids are all that remain over the summer months.
The distribution of Caladenia argocalla is estimated to have declined by at least 80 percent in the last 50-100 years. This decline is mainly attributed to habitat loss and fragmentation caused by land clearance and degradation.
Weed invasion is currently the most significant threat to Caladenia argocalla. Topped Lavender is a serious threat to all populations in the Clare Valley region, especially Sevenhill scrub. Vegetation clearance, herbivory, lack of pollination, and inappropriate land management activities also threaten the species.
The Department for Environment and Heritage (DEH) is working with landholders and community groups to implement on-ground recovery actions for Caladenia argocalla. It is vital that Sevenhill nature reserve is adequately protected and managed for biodiversity conservation. It is particularly important that a weed control program is implemented, using minimal disturbance ‘bushcare’ techniques such as cutting and swabbing.
Volunteers cutting and swabbing Topped Lavender. Photo: Joe Quarmby
List of other Environmental Initiatives Sevenhill Cellars
Solar power at the College, Winery and Retreat house
65ha of protected nature reserve containing endangered and threatened species. Management strategies are undertaken in partnership relations with:
- Department of Environment and Natural Resources,
- Natural Resources Northern and Yorke,
- Natural Resources Northern and Yorke volunteers’ group
- Trees for life
Initiatives include:
- Regular flora and fauna monitoring with documented counts
- Regular noxious weed control measures through volunteers, government grants and PIRSA weed control program participation.
- Professional advice and care to maintain and improve an environment essential to the existence of a population of threatened native orchids.
Minimal tillage techniques used throughout the vineyard to prevent soil erosion and build soil health.
Minimal irrigation used to prevent salt related soil issues and retain native water for native eco systems.
Capital spent on infrastructure to restrict use of imported water which would add additional salt to the soil from outside of the local area. (Mulching under vine and using drought-tolerant rootstocks on planting material
Restricted use of chemical-based fertilisers particularly nitrogen which if used adds to greenhouse gas emissions.
Parasitic mistletoe has been removed from some trees located around the Sevenhill College site.
Separation of paper, cardboard, glass, and plastics from the waste for recycling is standard practice.