Author(s): Grace McFarlane
Mentor(s): Micheal C. Rotter
Institution UVU
Thimbleberry (Rubus parviflorus) is a native shrub to North America, and plays a valuable role in ecological restoration. However, they have hard seed coats that result in low germination rates, which prevents efforts to establish genetically diverse populations in restoration projects. To help with this, we tested six germination treatments on Thimbleberry seeds from five populations in North America: standard planting (control), cold stratification, sandpaper scarification, hot water bath, sulfuric acid bath, and an overnight soak in room-temperature water. Our results indicated overall low germination, with no populations exceeding 10% except the sulfuric acid bath treatment, which achieved a germination rate of approximately 19% and showed the fastest germination onset. We recommend sulfuric acid bath as the preferred method for Rubus parviflorus seed propagation in restoration projects. These findings suggest that the sulfuric acid treatment effectively weakens the seed coat, increasing germination percentage, and potentially simulates natural dispersal processes, such as ingestion by frugivores. A second trial based on our results focusing on sulfuric acid, sulfuric acid plus overnight soak, and sandpaper plus overnight soak is ongoing to further refine these protocols.