Christmas Cactus

The Christmas cacti are a group of bushy perennial cacti growing to a height of about 15 cm (6 in). These cacti are often found in shaded areas in rich, well-drained soils.

John Kaprielian/Photo Researchers, Inc.

Organ Pipe Cactus

The organ pipe cactus grows in parts of Arizona, Baja California, and northern Mexico at elevations below 1,000 m (3,000 ft). The organ pipe reaches a height of 6.6 m (20 ft) and has white flowers and red fruit.

Stan Osolinski/Oxford Scientific Films

Saguaro Cactus 

The saguaro cactus grows in parts of Arizona, eastern California, and northern Mexico at elevations below 1,200 m (4,000 ft). One of the largest of the cactus species, the saguaro reaches a height of 12.2 m (40 ft) and has spines up to 7.6 cm (3 in) long. Its white flowers generally open only at night. The fruit is red.

Phil Lauro/ProFiles West

Prickly Pear Cactus

The prickly pear cactus is found throughout the southwestern United States, Baja California, and the Sonoran Desert region of Mexico. It is widely naturalized in many other areas, including Europe and Australia. Prickly pears have whitish, yellow, orange, or red flowers and greenish-brown, yellow, yellowish-green, red, or purple fruit, which are suitable for human consumption. The cactus plants themselves are also edible and are commonly used for livestock feed.

D. Wrigglesworth/Oxford Scientific Films

Jumping Collar Cactus

The jumping cholla, native to rocky deserts and hillsides of Baja California, northern Mexico, Arizona, and New Mexico, grows to a height of 5 m (15 ft). The plant has lavender flowers and a greenish fruit that grows in a chain-like fashion over a period of years.

T. Middleton/Oxford Scientific Films

Saguaro Forest

Saguaro National Park in Arizona includes forests of saguaro cacti or giant desert cacti. The saguaro cactus can live to be 200 years old, reach heights of around 15 m (50 ft) , and weigh as much as 9 metric tonnes. It grows extremely slowly, however, and after 50 years it may only be 2.1 m (7 ft) tall.

Matt Bradley/Bruce Coleman, Inc.

Cactus and Spurge Plants

Although all three of the plants in this picture appear to be cactus plants, the one to the far left is a spurge, not a true cactus. While both the cactus and the spurge have reduced, spiny leaves to prevent water loss, and a large, succulent stem for water storage, they are quite different plants, distinguished by the presence of a milky latex-like fluid in the stem of the spurge. This similar adaptation to their arid environment is an example of convergent evolution.

Dorling Kindersley

Barrel Cactus

Various species of barrel cactus in the genus Ferocactus grow in parts of Baja California, Mexico, Arizona, and California at elevations below 2,000 m (6,000 ft). Depending on the species, barrel cactus plants reach a maximum size of 1.5 to 3 m (5 to 10 ft). The flowers are generally a yellow, greenish-yellow, purplish-red, or orange colour.

Stan Osolinski/Oxford Scientific Films

Web Links

The Cactus & Succulent Plant Mall

The Cactus and Succulent Plant Mall