Ronald Stewart Byles

Pilosocereus (from Latin, "hairy cereus") is a genus of cactus native to the Neotropics. Tree cactus is a common name for Pilosocereus species. The genus Pseudopilocereus is a synonym of this genus. For many years, the illegitimate name Pilocereus was used for this genus, although properly a synonym for Cephalocereus. The subdivision of the genus has varied very widely, resulting in very different numbers of species being accepted. The commonly cultivated Pilosocereus pachycladus (syn. Pilosocereus azureus) is a blue cactus with hairy areoles that emit golden spines.

Pilosocereus polygonus is a species of cactus (family Cactaceae). Like all species in the genus Pilosocereus, it has a shrub- or tree-like growth habit. It has been treated very differently at times. In the narrow circumscription adopted here, it is endemic to Hispaniola, a position adopted by Britton and Rose in 1920 and endorsed in a 2019 review of the genus in the Caribbean and northern Andes. Treatments in the late 1990s and early 2000s used a much broader circumscription, which included species now recognized as separate, thus giving P. polygonus a much wider distribution. As of July

Pilosocereus leucocephalus, called old man cactus (along with a number of similar species), old man of Mexico, tuno, and woolly torch, is a species of cactus in the genus Pilosocereus, native to Mexico and Central America. It has gained the Royal Horticultural Society's Award of Garden Merit. Pilosocereus leucocephalus functions as a keystone species in dry landscapes found in Mesoamerica. The fruit this cactus produces is relied upon as a source of hydration and sugar in arid areas by frugivores such as birds, bats, and even some reptiles.

Pilosocereus catingicola is a flowering plant in the family Cactaceae that is endemic in northeastern Brazilian states of Rio Grande do Norte, Pernambuco, Alagoas, Sergipe, Paraíba, Bahia. The plant is bat-pollinated, by Goldman's nectar bat.

Pilosocereus piauhyensis is a species of plant in the family Cactaceae. It is endemic to Brazil, in the states of Piauí, Ceará, and Rio Grande do Norte. Its natural habitat is rocky areas.

Pilosocereus pentaedrophorus is a species of tree cactus found in Bahia and Minas Gerais, Brazil.

Pilosocereus lanuginosus is a species of flowering plant in the cactus family Cactaceae, native to Aruba, Bonaire, and Curaçao in the Leeward Islands. It was first described by Carl Linnaeus in 1753 as Cactus lanuginosus.

Pilosocereus glaucochrous is a species of plant in the family Cactaceae. It is endemic to eastern Brazil, in central Bahia state. Its natural habitat is subtropical or tropical dry forests. It is threatened by habitat loss.

Pilosocereus floccosus is a species of plant in the family Cactaceae. It is endemic to Brazil, in Bahia and Minas Gerais states. Its natural habitats are subtropical or tropical dry forests and rocky areas. It is threatened by habitat loss.

Pilosocereus chrysacanthus is a species of Pilosocereus found in Mexico to Honduras

Pilosocereus auristetus is a species of cactus native to Minas Gerais, Brazil and was first described in 1957.

Pilosocereus arrabidae is a species of plant in the family Cactaceae. It is endemic to Brazil. Its natural habitats are rocky shores and sandy shores. It is threatened by habitat loss.

Pilosocereus chrysostele is a species of Pilosocereus found in Brazil

Pilosocereus robinii is a species of cactus known by the common name Key tree-cactus. It is native to the Florida Keys in the United States, northwestern Cuba, and the north of The Bahamas. It has been erroneously reported from Puerto Rico, the Virgin Islands, and Mexico.

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Pilosocereus alensis, the Sonoran old man cactus, is a species of cactus native to Western Mexico, from Sonora south to Jalisco. The hairs protect the flower buds. Flowers open at night in June and give off the odor of ammonia, attracting bats for pollination.

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Pilosocereus collinsii is a species of cactus native to Oaxaca, Mexico.

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Pilosocereus millspaughii, commonly called the Key Largo tree cactus, is a species of flowering plant in the family Cactaceae, native to The Bahamas, Cuba, Haiti, and the Turks and Caicos Islands. It was also native to Florida, but is now locally extinct there due to sea level rise. It was first described by Nathaniel Lord Britton in 1909 as Cephalocereus millspaughii.

Pilosocereus colombianus is a species of cactus (family Cactaceae) native to Colombia, Ecuador and Peru. It was first described in 1909.

Pilosocereus moritzianus is a species of flowering plant in the cactus family Cactaceae, native to Trinidad and Tobago and the Venezuelan Antilles in the Caribbean and to Venezuela in northern South America. It was first described in 1837 as Cereus moritzianus. It was subsequently placed in the genus Cephalocereus before being moved to Pilosocereus in 1957. It has also been treated as a subspecies of Pilosocereus lanuginosus, P. lanuginosus subsp. moritzianus.

Pilosocereus brooksianus is a species of flowering plant in the cactus family Cactaceae, endemic to Cuba. It was first described in 1912 by Nathaniel Lord Britton and Joseph Nelson Rose as Cephalocereus brooksianus.

Pilosocereus catalani is a species of cactus native to an unknown location.

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