Neobuxbaumia
Neobuxbaumia is a genus of tall, columnar cacti native to Mexico, several of whose species grow into towering, tree-like giants of the tropical dry forest. Depending on the species, plants may stay solitary and unbranched for many years or eventually branch to form a candelabra-like crown, and the largest kinds rank among the most imposing columnar cacti in the country's arid lowlands. The genus is closely allied to Cephalocereus and Pachycereus, and its ribbed green columns are a familiar sight rising above the thornscrub of central and southern Mexico.
Description
Members of Neobuxbaumia are ribbed, columnar cacti with firm, upright, green to blue-green stems. Young plants and many mature ones remain unbranched, forming a single tall shaft; some species branch only high up with age, producing a small candelabra of vertical arms. The stems carry numerous shallow to prominent ribs lined with closely spaced areoles bearing short spines, which in most species are modest rather than fierce.
Flowers are borne near the stem tips, often opening at night or around dusk and lasting a short time. They tend to be tubular or bell-shaped in muted tones of pink, purple, greenish-white or cream, and are pollinated in habitat by bats as well as by insects and birds. The fruits are fleshy and carry numerous small black seeds. As with many large columnar cacti, plants must reach considerable size and age before they begin to flower.
Distribution
Neobuxbaumia is endemic to Mexico, where its species occur through the central and southern states in seasonally dry tropical forest, thornscrub and arid valleys. Several are characteristic of the semi-arid Tehuacán–Cuicatlán region and neighbouring lowlands, where they can dominate the landscape as columnar "forests." Plants grow in gritty, well-drained soils on slopes and plains that are hot for much of the year and receive rain in a distinct summer season.
Notable species
- Neobuxbaumia polylopha — the golden cactus, a solitary, many-ribbed column clothed in golden spines; one of the most ornamental species and popular in cultivation.
- Neobuxbaumia tetetzo — a tall, branching species that forms extensive columnar stands in the Tehuacán Valley.
- Neobuxbaumia scoparia — a slender, densely branched columnar cactus of southern Mexico.
- Neobuxbaumia mezcalaensis — a robust column from the arid valleys of the Mezcala region.
- Neobuxbaumia macrocephala — a large species notable for the woolly, cephalium-like flowering zone it develops near the stem tip with age.
Cultivation
As a group, Neobuxbaumia are grown much like other large columnar cacti and are generally undemanding given warmth and drainage. Provide a very free-draining, mostly mineral mix and a pot deep enough to anchor the growing column. Give bright light and as much sun as you can, which keeps growth compact and the spination strong; plants raised in too much shade tend to etiolate and grow thin.
Water generously during the warm growing season once the soil has dried, then reduce sharply and keep the plant dry through the cool months. These are frost-tender, lowland plants: protect them from freezing temperatures and keep them on the warm side in winter. Tall specimens become top-heavy, so a heavy pot and eventual repotting into a stable container help prevent toppling. See Watering for general technique.
Hobby and cultivar notes
Neobuxbaumia polylopha is by far the most commonly grown species and is prized for its golden, ribbed column; the others are more of a specialist's interest but appreciated by collectors of large columnar cacti. Plants are almost always raised from seed, and named cultivars are few. As with many columnar genera, growers occasionally use vigorous species as grafting stock, and seedlings can be sped along considerably under good warmth and light. Because these cacti ultimately want to be big, they suit growers who can offer greenhouse height or a warm, bright, frost-free spot outdoors.
Propagation
Seed is the primary and most reliable method: sow onto a warm, damp mineral surface and keep humid until the seedlings establish, then grow them on in bright light. Branching species can sometimes be increased from stem cuttings, which should be left to callus well before potting into a dry, gritty mix; solitary, unbranched kinds offer little scope for vegetative propagation. See Propagation — seed and Propagation — cuttings for full walkthroughs.
See also
- Cephalocereus · Pachycereus — closely related columnar genera
- Soil and potting mix · Watering · Repotting
- Propagation — seed · Propagation — cuttings · Grafting
- Pests and diseases