Cephalocereus spp.

old man cactus

Cactaceae Mexico

Attracts Pollinators Deer Resistant Drought Tolerant Container Friendly

Native to North America

SunFull Sun

WaterVery Low · drought-tolerant

HardinessZones 9–11

Overview

Cephalocereus spp. is a genus of columnar cacti in the family Cactaceae, native to Mexico. The most familiar species, C. senilis, is covered in long white or grey hairs that veil the green, ribbed stem beneath. Stems are unbranched or sparingly branched and grow slowly, reaching 15 to 50 feet (4.5 to 15 m) over many decades in habitat, though cultivated plants rarely exceed a few feet. The hairs are modified spines that shade the stem surface and insulate it against heat and cold, growing longest near the stem tip. Sharp yellow spines lie hidden beneath the wool. Mature stems develop a lateral flowering zone called a cephalium, a dense mass of wool and bristles from which the flowers emerge. Funnel-shaped flowers, 2 to 3.5 inches (5 to 9 cm) long, open at night in cream, pink, or pale yellow and are followed by rounded fleshy fruits. Plants take many years to reach flowering size, and the cephalium forms only on old stems. The genus stores water in its thick stem tissue, letting it endure long rainless periods in its arid limestone habitats.

Native Range

Cephalocereus spp. is endemic to Mexico, where species grow on arid limestone slopes and in tropical dry scrub, chiefly in the states of Hidalgo, Guanajuato, Veracruz, and Oaxaca. C. senilis occupies steep canyon walls in central Mexico.

Suggested Uses

Grown as a specimen in cactus and succulent collections, desert-style plantings in frost-free regions, and as a container plant elsewhere. The slow, columnar form suits rock gardens and gravel beds in arid climates.

How to Identify

Tall, unbranched ribbed stems are cloaked in long white to grey woolly hairs, densest toward the growing tip. Beneath the wool lie rows of sharp yellow spines along the ribs. Old stems form a woolly lateral cephalium near the top from which night-opening flowers arise.

Appearance

Size & Dimensions

Height15' - 50'

Width/Spread1' - 1'6"

Colors

Flower Colors

Fall Foliage Colors

Bloom Information

Bloom Period

~4 weeks

Spring Summer

Flowering occurs in late spring and summer once a stem is mature enough to form a cephalium, a stage that can take 10 to 20 years or more. The funnel-shaped flowers open at night and close by midday. Many cultivated plants never reach flowering size indoors.

Detailed Descriptions

Flower Description

cream, pink, or pale yellow

Growing Conditions

Sun Requirements

SunFull Sun

Requires 8-12 hours of direct sunlight daily

• Full Sun: 6+ hours of direct sunlight

• Partial Shade: 3-6 hours of direct sunlight

• Full Shade: Less than 3 hours of direct sunlight

Soil Requirements

pH Range6.0 - 7.5(Neutral)

357912

Soil Types

sand rocky loam

Drainagewell drained

Water & Climate

Water Needs

Very Low

Frost Tolerance

tender

Time to Maturity

10-20 years to flowering

Drought Tolerance

Drought tolerant when established

Care & Maintenance

Care Guide

Plants grow in full sun and sharply draining mineral soil, such as a cactus mix amended with extra grit or pumice. Moderate watering suits the warm growing season, with nearly dry conditions through winter when stems rest. Minimum safe temperatures sit around 50F (10C), so in frost-prone climates plants are grown in containers and moved under cover for winter. The long hairs collect dust over time and can be rinsed gently with water. Overwatering in cool conditions leads to basal rot, the most frequent cause of loss in cultivation. Strong light keeps the wool dense and the stem firm.

Pruning

Routine pruning is not needed. Damaged or rotted sections can be cut back to firm green tissue with a clean blade, and cut surfaces left to callus before watering resumes. Offsets, where produced, can be removed for propagation.