Type 2 - Barrel Cactus. Single fat stem that is globular or columnar.
Barrel cactus are some of the most eye-catching
plants because of the unusual size and shape. They don't look like any
other plants in there habitat, with their fat round bodies; and they
can become quite large. Barrel cactus take on a globular shape when
young, which could be more than 30 years. Then, most will become
columnar. It is possible to have a barrel cactus that is two feet wide
by seven feet tall.
Two of the most popular genera of barrel cactus are
Echinocactus and Ferocactus. Most people have heard of the Golden
Barrel cactus (Echinocactus grusonii), which can grow to be 24 inches
wide the 36 inches tall. However, there is Echinocactus platycanthus,
which can mature at 30 inches wide and 84 inches tall. We have all
heard of the Fish Hook cactus (Ferocactus wislizeni). But what about
Ferocactus diguetii that can reach up to 12 feet tall (3.6 m), 3 feet
in diameter (90 cm).
As with hedgehogs there are also contrasts in size
with barrel cactus. Some of the smaller ones are Echinocactus texensis,
E. horizonthalonius, Ferocactus latispinus, and F. viridescens.
Many the South American cactus species also form a
barrel shape, such as Gymnocalycium saglionis, Notocactus herteri, and
Echinopsis bruchii (Soehrensia bruchii).