I've heard of Amy Greenwell botanical garden. I've never been there but my parents went there and brought home (O'ahu) some seeds. Depends what you're interested in though. If you'd like to see native plants there are many places on the big island you can go. Much of the big island's wilderness landscape is dominated by native vegetation (in Hawaii it is not easy to find native dominated landscape). Hawaii Volcanoes National Park has several places were you can find unique Hawaiian plants - most of the park is native vegetaion.

Here is a link that might be useful: Big Island Botanical Gardens

Thanks for the info ... appreciated.

Good Day ...