Bark coverage occurs on stems of more than twenty species of columnar cacti. This report documents characteristics of areoles and spines from central Mexico with bark coverage percentages on five columnar cactus species (Cephalocereus columna-trajani, Neobuxbaumia macrocephala, N. mezcalaensis, N. tetetzo, and Pachycereus hollianus). Older cacti (more than 4 m tall) had fewer original spines than younger cacti (less than 2 m tall). For cacti taller than 4 m, loss of the original spines was positively correlated with bark coverage. For three species, loss of the original spines occurred with about 75% for bark coverages. Four of the five species studied produced hair-like spines at areoles. Three of the five species produced emergent spines. Most emergent spines were associated with hair-like spines. The presence of hair-like and emergent spines (spines that emerged on mature cactus surfaces) was not well correlated with percentages of bark coverage. Hair-like spines have been noted previously, but no function has been attributed to them. This is the first report with a description of emergent spines on tall, long-lived columnar cactus species.