DOWNTOWN. Once the private realm of German-born doctor William Hillebrand and his wife, these gardens were begun in the mid-19th century on land leased from the queen. Added to by subsequent residents, the gardens were donated to the city in the 1930s and given over to public use. Over the next several decades, thousands of plants were added, and the gardens now occupy 14 acres and feature a number of endangered species. Along with fascinating tropical plants, you'll find collections of orchids, "exceptional trees," and plants known for their domestic utility.

MANOA VALLEY. At almost 200 acres, this university-affiliated arboretum seeks to increase knowledge and awareness of tropical plant species. More than 7500 types of plants occupy the grounds, including considerable collections of native Hawaiian species and palms. As part of its mission, the arboretum strives to preserve endangered specimens and also brings to the public new, ornamental plants that it cultivates. Established paths through the grounds allow folks to wander among the plantings and to appreciate the birds that make their home there as well.