I think it's better to end up without the information than to get too general and provide misleading information. The zones and size ranges can be filled in by hand for each individual entry, just as they always were before. Ideally, this could be done at some point by the person submitting the mass proposal. That's in line with my adopt-a-plant philosophy.
Choose a genus and species, submit a mass proposal for common features, and then add as much specific data as possible to each individual entry.