Puʻu Kukui is a mountain peak in Hawaiʻi. It is the highest peak of Mauna Kahalawai (the West Maui Mountains). The 5,788-foot (1,764 m) summit rises above the Puʻu Kukui Watershed Management Area, an 8,661-acre (35.05 km2) private nature preserve maintained by the Maui Land & Pineapple Company. The peak was formed by a volcano whose caldera eroded into what is now Īʻao Valley.
Puʻu Kukui is one of the wettest spots on Earth and the third wettest in the state after Big Bog, Maui and Mount Waiʻaleʻale, receiving an average of 386.5 inches (9,820 mm) of rain a year. Rainwater unable to drain away flows into a bog. The soil is dense, deep, and acidic.Puʻu Kukui is home to many endemic plants, insects, and birds, including the greensword (Argyroxiphium grayanum), a distinctive bog variety of ʻōhiʻa lehua (Metrosideros polymorpha var. pseudorugosa) and many lobelioid species. Due to the mountain peak's extreme climate and peat soil, many species, such as the ʻōhiʻa, are represented as dwarfs. Access to the area is restricted to researchers and conservationists.