Etymology -From the Greek word pachys, meaning thick and the Latin word cereus, meaning candle.
The genus Pachycereus contains some of the largest growing cacti of all. One species is reported to reach a height of 82 feet (25m) in height! Although not all species are quite that large, all of them are columnar and feature tree-like or shrubby growth with relatively large branches.
Stems are ribbed and may be either a blue-green or bright green color. Like most columnars, 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.
Flowers are are small tubes or funnels up to 4 inches long. The floral tubes feature scales and may be bare, fuzzy, or spiney. Fruits are dehiscent and fleshy.
Two species, P. pringlei and P. marginatus are extremely common in cultivation. The former is a native of Baja California and is often confused with the well-known "Saguaro", while the later is grown in Mexico in tight lines as a "living fence". Perhaps 2 or 3 other species are found in a limited number among collectors or grown in yards near their native habitat. However, the remaining species are almost non-existent in cultivation.
In Mexico and nearby Central America where all species are found, there are entire forests of Pachycereus. Yet, it seems there is very little interest in these plants are cactus lovers who visit these areas, seem to ignore the towering giants in search of the small globose species which hide themselves among the rocks.