Cephalocereus senilis aka Bunny Cactus

Cephalocereus senilis is a long-lived cactus called old man cactus. It belongs to the cactus family, Cactaceae. Its native range lies in northeastern Mexico, reaching Veracruz. It grows in dry scrub, limestone hills, and canyons. Wild plants face pressure from collection and loss of habitat. Taking young plants from the wild threatens their future numbers. Growers also raise this species from seed for sale.

This upright succulent forms tall columns, sometimes branching at the base. Houseplants reach about 3–4 feet [0.9–1.2 metres] tall. Their spread ranges from 0.5–1 foot [0.15–0.3 metres]. Wild plants can reach 40 feet [12.2 metres]. LLIFLE reports taller plants near 49 feet [15 metres]. Growth is slow, though good summer care can speed it. The round-topped stems start green and turn gray with age. Each stem can grow about 1 foot [0.3 metres] thick. Long white bristles give young plants their woolly look. These bristles are modified spines that shield stems from sun and cold. Older stems lose some of this cover. Sharp yellow spines hide beneath the soft-looking coat.

Plants may wait 10–20 years before they first flower. Mature stems form a dense woolly flowering zone near the top. The flowers open at night and have a funnel shape. Their colors include red, pink, yellow, and white. Chicago Botanic Garden lists bloom from May through August. Rose-colored fruits develop three to four weeks after flowering. They have a narrow base and a broader rounded end. Each fruit holds many black seeds. House finches eat the fruits and seeds, helping spread them. Plants seldom form fruit indoors.

Give this cactus full sun outdoors and strong light indoors. Indoor plants also need some direct sun. Move plants into stronger light in stages to prevent sunburn. Use a fertile soil mix that drains well. Water deeply, then let the mix dry before watering again. Withhold water and feed in winter. Monthly balanced feed supports growth during the growing season. Sources place it in USDA zones 9–11. It still needs shelter from frost and freezing weather.

Its pale coat makes it useful as a container accent. It also suits rock gardens and succulent beds. Deer tend to leave it alone. Mealybugs and scale can hide beneath the bristles. Too much water can cause fungal disease and root rot. Cold, damp conditions also harm it. ASPCA lists it as non-toxic to cats, dogs, and horses. Its sharp spines remain a risk when handling it.