Key tree cactus

Pilosocereus robinii is a large cactus growing erect, often with many parallel or spreading branches. It may become a tree up to 10 m (33 ft) tall. The stem is green in color with a blue tinge when young and has 9 to 13 ribs. The areoles are covered in long or short hairs and have up to 31 spines each. The spines are no more than a centimeter long. The bell-shaped flower is 5–6 cm (2.0–2.4 in) long. The outer tepals are greenish with brownish midstripes and the inner tepals are white. The flower has a scent similar to garlic. It opens at night and contains a sweet nectar.

Pilosocereus robinii is native to the north of The Bahamas (Andros and Cat Island north to Abaco), northwestern Cuba (the provinces of La Habana, Matanzas, and Mayabeque), and the United States (the Florida Keys). It is the only Pilosocereus species native to the United States. In the Florida Keys, P. robinii grows in upland tropical hardwood hammocks on limestone or coral substrates. It sometimes grows on sparsely vegetated coral rock and just above the high tide mark. Few of these plants produce fruits. Their seeds are dispersed by frugivores. Windy conditions also spread the seeds and can also break off branches which can root themselves in the soil. Storm surges and sea level rise may inundate its shoreline habitat and increase the salinity beyond the tolerable range for the cactus.