The D.T. Fleming Arboretum is Hawaii's oldest and largest native arboretum. It was planted in the Pu'u Mahoe cinder cone on Maui's southern slopes of Ulupalakua to preserve species from the dying forest of Auwahi.

Pu'u Mahoe was a gift to D.T. Fleming from Ed Baldwin of Ulupalakua Ranch. It was a reward for introducing a wasp to parasitize the Pamakani weed that was taking over the grazing lands. After years of introducing trees to Maui from around the world "to make Maui a better place to live," D.T. Fleming’s dream for retirement was to plant an arboretum for native species.

Throughout his life on Maui he witnessed the dryland forest of Auwahi going extinct due to cattle and drought. Fleming chose Pu'u Mahoe's cinder cone as a perfect place to preserve these species at the 2,600-foot elevation on the edge of the Auwahi Forest.

It took two years to prepare the area by building a caretaker’s cottage, fences and a water system. In 1952 propagated seedlings and air-layers from the Auwahi Forest were planted into the Arboretum. Fleming was able to enjoy the young trees flourish until his death in 1955 Over the next 45 years the Arboretum was cared for by Fleming's daughter Euphence and her husband Jack Vockrodt. For this dedication they received the Historic Preservation Award in 2001. Today, of the 150 species of native flora planted in the Arboretum, 33 of these are on Hawaii's endangered list. It is almost a complete collection of Auwahi Forest species and a valuable seed bank for their preservation.

The charitable foundation Friends of the Fleming Arboretum (FOFA) was created to support the Arboretum goals. FOFA is 501-c3 non-profit organiztion qualified to receive foundation grants and accept 100% tax-deductible donations.