Pachycereus is a genus of about 12 species of large cacti native to Mexico and just into southern Arizona, USA. They form large shrubs or small trees up to 515 m or more tall, with stout stems up to 1 meter in diameter. Pachycereus comes from the ancient Greek “pakhus” meaning “thick” and the Latin “cereus” meaning “torch”. The genus Pachycereus contains some of the largest growing cacti of all. One species is reported to reach a height of 25 meters! Although not all species are quite that large, all of them are columnar and feature tree-like growth. Stems are ribbed and may be either a blue-green or bright green colour. Like most columnar cacti, there is a considerable difference between smaller seedling plants and the larger mature plants. Often smaller plants will be heavily armed with spines which are reduced or even absent on older stems. A few exhibit a pseudocephalium – that is an area of extremely dense spines, which gives rise to the flowers. They do well in raised beds, rockeries and large pots.

Pachycereus pecten-aboriginum commonly known as hair brush or Indian comb is a columnar Organ Pipe type cactus tree, and is native to north western Mexico. The plant is leafless and can grow up to 15 m high. The trunk of this species is 1.2-5 m tall and the fruits are large and burlike. The species name, pecten-aboriginum, is from Latin, meaning native combs because the fruit were used as hair combs.