I am not an expert on this necessarily – but I think the reason that gardens are not typically the engine behind listing petitions has less to do with conflict of interest and more to do with skill set. For certain petitions, there might be legal or advocacy resources required to move the petition forward that a garden may be less likely to have as part of their mission compared to, say, a native plant society or more policy-focused nonprofit. However, I suppose it might be uncomfortable for a garden to petition for listing of a species if it’s somehow a contentious topic with a funding entity, but I don’t think that would stop “most of us”.  Is there a certain species you’re thinking about? Maybe we can have a breakout group about petitioning at the CPC National Meeting.