Pachycereus

This group consists of twelve, columnar-shaped cacti native to parts of the southern United States and Mexico. This group contains some of the largest-growing cacti; they range in height from 13 to 42 feet. Some have solitary stems but many branch to form clumps or even trees. Mature plants that are 6 to 15 years old bear flowers. The blossoms are funnel-shaped and tinged with white or pink. They only open at night and are produced at the stem tips in spring to early summer. They are followed by large, spiny, green, yellow, or red fruits. These cacti are great for growing in containers indoors and outdoors and as using for landscape plants. The most commonly seen is P. pringlei (Elephant Cactus; Mexican Giant). This species can grow up to 42 feet high, with a main trunk 2 feet thick. The mature branches are scarcely spined and bear 31/4-inch long, white flowers. In cultivation, this cactus can grow a foot in one season. It will not tolerate frost. P. schottii (Senita Cereus; Whisker Cactus) forms numerous stems that can grow up to 20 feet high and have a spread of 8 feet. When this species is about 6 feet high, its gray spines become long and curly at the stem tips. Its cream to dark pink flowers are followed by small, red berries. P. schottii var. monstrose (Totem Pole) is an interesting mutation thought to be caused by a virus. It is slow growing and rarely flowers but is valued for its weird, knobby stems, which can also grow up to 20 feet high.

Pot Cultivation

These cacti need a minimum temperature of 50� F and plenty of sun. They won't tolerate frost and will become scarred by excessive cold. Grow them in rich, porous, sandy soil and let their soil dry out between waterings. Repot, in the spring, when their roots become cramped; these cacti like large pots for free root growth. Generally, they should be repotted every other year in order to provide fresh soil. However, this doesn't necessarily mean they'll need larger containers. Fill about a quarter of the pot with broken crocks, gravel, etc. to promote good drainage. Firm the potting soil. After repotting, do not water for a week or more.

Propagation

Seeds should be used for propagation because the shoots are too thick to use as cuttings. The seeds may be sown in containers filled with a general-purpose cactus and succulent potting mix. Sprinkle the seeds evenly over the surface of the compost. Cover them lightly with some grit, moisten the container and place in an area with high humidity and warmth. Transplant the seedlings when they are large enough to handle. Waiting too long until they are overcrowded can cause rot. Gently separate them so as not to damage the delicate roots. Transplanting will be easier if the soil is slightly moist. Seedlings can be potted singly or with several to a pot. They seem to do better a few together than by themselves.

P. pringlei

VARIETIES

• P. pringlei;
• P. schottii & var. monstrose.