Pachycereus is a genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of 9–12 species of large cacti

Cactus

A cactus is a member of the plant family Cactaceae. Their distinctive appearance is a result of adaptations to conserve water in dry and/or hot environments. In most species, the stem has evolved to become photosynthetic and succulent, while the leaves have evolved into spines...

 native to Mexico

Mexico

The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...

 and just into southern Arizona

Arizona

Arizona ; is a state located in the southwestern region of the United States. It is also part of the western United States and the mountain west. The capital and largest city is Phoenix...

, USA. They form large shrub

Shrub

A shrub or bush is distinguished from a tree by its multiple stems and shorter height, usually under 5–6 m tall. A large number of plants may become either shrubs or trees, depending on the growing conditions they experience...

s or small tree

Tree

A tree is a perennial woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance. A minimum height specification at maturity is cited by some authors, varying from 3 m to...

s up to 5–15 m or more tall, with stout stems up to 1 m diameter.

Pachycereus comes from the ancient Greek "pakhus" meaning "thick" and the Latin "cereus" meaning "torch".

Selected species

• Pachycereus gatesii
• Pachycereus gaumeri
• Pachycereus grandis
• Pachycereus hollianus
• Pachycereus marginatus
  Pachycereus marginatus
  Pachycereus marginatus is a species of plant in the Cactaceae family....
  
  
• Pachycereus militaris
• Pachycereus pectin-aboriginum
• Pachycereus pringlei
  Pachycereus pringlei
  Pachycereus pringlei is a species of cactus that is native to northwestern Mexico in the states of Baja California, Baja California Sur, and Sonora...
  
  - Cardón cactus
• Pachycereus schottii - Totem cactus, senita cactus
• Pachycereus weberi

Pachycereus pringlei is the tallest cactus species in the world, with a maximum recorded height of 19.2 m (Salak 2000).

Synonymy
The following genera have been brought into synonymy with Pachycereus:

• Backebergia Bravo
• Lemaireocereus Britton
  Nathaniel Lord Britton
  Nathaniel Lord Britton was an American botanist and taxonomist who founded the New York Botanical Garden in the Bronx, New York. Britton was born in New Dorp in Staten Island, New York...
  
   & Rose
  Joseph Nelson Rose
  Joseph Nelson Rose was an American botanist. He was born in Union County, Indiana. His father died serving during the Civil War when Joseph Rose was a young boy. He later graduated from high school in Liberty, Indiana....
  
  
• Lophocereus (A.Berger) Britton
  Nathaniel Lord Britton
  Nathaniel Lord Britton was an American botanist and taxonomist who founded the New York Botanical Garden in the Bronx, New York. Britton was born in New Dorp in Staten Island, New York...
  
   & Rose
  Joseph Nelson Rose
  Joseph Nelson Rose was an American botanist. He was born in Union County, Indiana. His father died serving during the Civil War when Joseph Rose was a young boy. He later graduated from high school in Liberty, Indiana....
  
  
• Marginatocereus (Backeb.) Backeb.
• Mitrocereus (Backeb.) Backeb.
• Pterocereus T.MacDoug. & Miranda