Pu‘u Ku (Pu‘u Ki‘i) Islet is located in Hāna Bay just offshore from the main island of Maui. Pu‘u Ku is about 1.3 acres in size and reaches a height of about 60 ft. Pu‘u Ku is a mix of cinders and lava flows, part of the East rift of Haleakalā, and is barely detached from the main island. The islet is covered on the west side by ironwood (Casuarina equisetifolia) with a mix of naupaka (Scaevola taccada), maia pilo (Capparis sandwichiana), and ‘ānaunau (Lepidium bidentatum var. o-waihiense) on the steep north and east sides. The summit is a mix of sourbush (Pluchea carolinensis), ‘ūlei (Osteomeles anthyllidifolia), lantana (Lantana camara), laua‘e (Phymatosorus grossus), and naupaka (Scaevola taccada). Hala (Pandanus tectorius) is found scattered about the islet. Up to a thousand ‘ua‘u kani (wedge-tailed shearwater or Puffinus pacificus) burrow under the ironwood grove on the west side of the islet. Koa‘e kea (white-tailed tropic bird or Phaeton lepturus dorotheae) may nest there. Long legged ants (Pheidole megacephala) and unfortunately, hala scale (Thysanococcus pandani) have been found there.

As with all state Seabird Islet Sanctuaries, visiting Pu‘u Ku is prohibited. They are rare places where seabirds can nest with few or no predators and no large mammals (including humans) trampling and crushing the burrow where they raise their young. Turtles and seals can rest on their tiny shores without harassment and they are havens for native insects and plants without people constantly inadvertently bringing in weed seeds and other alien pests. Respect and admire these places through binoculars, peacefully, from shore.