When you first step off 
a plane at the Honolulu airport on the island of Oahu, the air, no matter what time of year it is, is scented with flowers and a hint of the sea. Hawaii truly is a garden paradise, and for my taste, the native plants rule. They are absolutely splendid, and there's always something in bloom. There are 
"exotic" tropical plants everywhere, in people's yards, in planters at store fronts, in median flower beds at malls and shopping center. The official state flower is the yellow hibiscus hibiscus brackenridgei, known as the pua aloalo in Hawaiian. The yellow hibiscus is a native plant, but there are a large number of hibiscus varieties and several colors that are flourishing in the islands. The islands each have their own official flower as well; in Oahu' the official flower is the yellow ilima Sida fallax, treasured for traditional medicine and for lei making. 
One of my personal favorites is the sweetly-scented white plumeria, which grows easily almost everywhere; you might know it as frangipani. You'll also notice orchids, native and transplanted, growing almost everywhere.
The Honolulu Botanical Gardens are an official city-owned collection of five gardens open to the public. The gardens are scattered across the island of Oahu, and there's no admission charge for visiting, except for at Foster Botanical Garden. Foster Botanical Garden is located in down town Honolulu; it is the oldest of the affiliated gardens. The garden contains 24 "exceptional trees," some going back to the 1800s, as well as a Palm collection, the Lyon Orchid Garden, a special Hybrid Orchid Display Case, and a carefully preserved Prehistoric Glen of native plants in their natural habitat. You can find out about admission, hours and guided tours here. You can read about visitors' impressions and see photos here.
Ho`omaluhia Botanical Garden is on four hundred acres in Kaneohe, on the windward side of Oahu, and you can drive through parts of it, as well as stroll on foot. Ho`omaluhia Botanical Garden features examples from tropical regions around the world, in specially grouped regional plots. There's a special interest and emphasis on conserving and propagating native Hawaiian plants. There are also camping grounds, and picnic facilities.
Koko Crater Botanical Garden is still very much a work in progress. It consists of 200 acres on the slopes and basin of Koko Crater at the eastern end of Oahu. The plan is to create examples of xeriscape landscaping, where plant species choices and water conservation techniques create a garden where plants suitable to desert-like surroundings on the crater slopes and basin will flourish and propagate. At present, there are no visitor amenities at all, no water fountains, or even restrooms. There is a large collection of plumeria and bougainvillea which bloom quite flamboyantly along the outer crater. There's also a somewhat steep two-mile long looping foot trail through the beginning collections of dryland plants.
Lili`uokalani Botanical Garden is also in downtown Honolulu between North Kuakini and School Streets. The start of this 7 and a half acre garden was the private garden and picnic grounds of Hawaii's last monarch, Queen Lili`uokalani.
Wahiawa Botanical Gardens 
are in central Oahu, between the Waianae and Koolau mountain ranges. This 27 acres of planned garden, part of which are in a forested ravine, began in the 1920s when a group of sugar planters used the site as an experimental arboretum. The collection is especially rich in native plants, and features a self-guided walking tour
There are also botanical gardens on the rest of the Hawaiian islands. On the Big Island of Hawaii there's the non-profit Hawaii Tropical Botanical Garden. This is a labor of love, and quite fabulous. It's worth making a special overnight trip just to see it. The Hawaii Tropical Botanical Garden is about 8 1/2 miles north of Hilo on the four-mile Scenic Route along the lush Hamakua Coast near Onomea Bay. The Garden is off of Highway 19. Drive along the scenic route, slowly, and then spend the rest of the day at the Garden. The Garden is a living botanical and bird museum contained in a forty acre valley. There are over 2,000 species, representing more than 125 families and 750 genera.
Thankfully, the lovely Forget-Me-Not can be found all over North America. This delicate blue flower is one of the most popular plants in traditional folklore, from biblical legend to German superstition. Lovers used to believe that if they wore the flower, they would always be remembered by each other. That’s much more romantic than putting your lover’s photo on your laptop’s screensaver or his favorite rap song as your ringtone, don’t you think? Sometimes the old customs can be more fun—and more simple—to follow.
