These are the gardens we enjoy while on Kauai:
Allerton National Tropical Botanical Gardens - Visitor's Center is across the road from Spouting Horn blowhole, Po’ipu; 2 ½ hour guided tour; need reservations; beautiful rich lush gardens, many scenes from the Jurassic Park movies were shot here; some history of Queen Emma, and Mr. Allerton. Also did the “behind the scenes” tour.
Kauai’s Hindu Monastery- on Kaholalele road off Kuamo’o Road (RT 580) on way to Opeka’a Falls; best if done via one of their tours, check web for dates and time; gardens and temple; Note: no shorts, no tank tops, etc on anyone
Limahuli National Tropical Botanical Garden - west of Hanalei; can walk through yourself or take guided tour (reservations needed); walked it ourselves; very interesting; more a Hawaiian cultural & history garden;
McBryde National Tropical Botanical Gardens - Visitor's Center is across the road from Spouting Horn blowhole, Po’ipu (same as Allerton); self-walk or guided tour call for reservations.
Na `Aina Kai Botanical Gardens & Sculpture Park - 4101 Wailapa Road, Kilauea; make tour reservations; did the formal and informal gardens (longer tour);