KOKO CRATER- amazing and it’s free! Inside an extinct volcano. Bring good sneakers/hiking shoes. The mini ecosystem inside the volcano is arid and dry and therefore they have lots of desert type plants and trees (Africa and Arizona all in 1). SO UNIQUE FOSTER- amazing. Mostly tropical and in the city so easy to get to. They have the corpse plants that only bloom so often and are super famous there. Take a guided tour!!! There is a small fee to get in, but so worth it. WAHIAWA- very good. I think it's 99% native Hawaiian plants/trees, so it makes for a very authentic experience! Located in the middle of the island. HO'OMALUHIA- good. East side of the island. Large and spread out. It's very peaceful and very wet. In fact, after a big rain, you can see dozens of waterfalls from here looking into the mountains. There are cooler things to do on this side of the island than this place, but it is still nice. It is free, if you wanted to take a peak anyways! LILI'UOKALANI- skip.
I cannot recommend the Bishop Museum enough! They have some amazing regular exhibits and also rotating, very focused on Hawaii, new and old. Open daily: 9AM-5PM $25 admission fee
I highly recommend a tour of the Iolani palace. The only royal building in the "U.S." It's so iconic and you get a lot of history of how the Hawaiian islands became part of the U.S. Queen Emma's Summer Palace is much lesser known, but wonderful. The tour guides there are amazing.
It's part of the University of Hawaii and obviously focuses on the trees, but there are some amazing ones out there (see: monkeypods).
Check out the breadfruit trees. Very famous in Hawaii. Also found in lots of art and symbols and on hawaiian quilts. THEN find a restaurant that serves breadfruit fries!! Square barrels in downtown Honolulu used to, but I'm not sure they have them anymore.
Open 9:30AM-4:30PM Closed Wednesdays GET DOLE WHIP! Do I have to pay to shop in the store or buy Dole Whip? There is no admission to enter the Visitor Center. The only admission is for the 3 Attractions (train, maze, garden).