Bringing Australia’s vulnerable Wittsteinia vacciniacea F.Muell. (Baw-Baw berry) into cultivation

Wittsteinia vacciniacea F.Muell. (Baw-Baw berry) is a vulnerable evergreen trailing shrub dating back over 70 million years, when Australia separated from Gondwanaland during the late Cretaceous period. It is the only species of Wittsteinia to occur in Australia, and one of four genera in Alseuosmiaceae. The Baw-Baw berry is restricted to a few mountainous populations of varying size and occupancy within Victoria. The fragrant flowers are attractive pendent yellow-red bells, and the globose fruit a greenish-red berry with persistent attractive calyx lobes. It is the combination of a trailing habit and floral features that make this species an ideal candidate for amenity horticulture. To test this, we collected plant material from five of the six known localities in Victoria and, using stem/cutting material with +/- Clonex® gel and either Jiffy® Plugs or a perlite/vermiculite mix +/- Clonex®, achieved 60.8 per cent root initiation overall. Greater root development was achieved using the plugs, and there were differences between root initiation and species locality. The hormone treatment proved unnecessary to ensure root initiation. To test germination response, seed was collected from Mt Baw Baw, which supports the largest population. Preliminary work on fresh seed indicated a high fill rate, determined by x-ray imagery, and a 90 per cent germination response at 20/15 °C with gibberellic acid (GA3). We explored the germination niche using a thermogradient plate and determined an optimal temperature of ~17 °C. Resulting vegetative and seed-based propagules have been incorporated into the Royal Botanic Gardens Victoria living collection, as part of a broader ex situ conservation strategy. Further to this, using predictive modelling, we found areas outside this species’ current distribution that may be suitable for future plantings, ensuring the Baw-Baw berry’s survival beyond its current refugia.