Pachycereus
Pachycereus is a genus of large columnar and tree-like cacti native to Mexico and adjacent regions, containing some of the most massive cacti in the world. Its name comes from the Greek pachys ("thick"), a nod to the stout, heavily ribbed stems that in the biggest species rise into branching, tree-sized giants. The genus includes iconic plants such as the cardón — often cited as the largest cactus species — and the curious, smooth-stemmed, ribless totem-pole cactus prized by collectors.
Description
Pachycereus are columnar cacti that range from tall single or few-branched columns to broad, tree-form giants with a distinct woody trunk and a candelabra of upright arms. Stems are stout, blue-green to grey-green, and carry numerous prominent ribs lined with closely set areoles. Most species are well armed with stiff spines, though the density and colour vary widely, and some famous forms (see below) are nearly spineless.
Mature plants can be enormous — the largest species reach well over ten metres tall and live for more than a century. Flowers are typically funnel- to bell-shaped, opening at night or around dawn, and are pollinated by bats, moths and birds; they are often followed by spiny, sometimes edible fruits. As with most tree cacti, plants must reach a considerable size and age before they flower.
Distribution
The genus is centred on Mexico, with its greatest diversity in the arid northwest — especially the Sonoran Desert and the Baja California peninsula — extending into parts of central and southern Mexico. Plants grow in hot, dry scrub and desert on rocky or sandy ground, where their ribbed columns expand and contract to store water through long droughts. Several species are important structural plants in their landscapes, forming "forests" of giant columns that shelter and feed desert wildlife.
Notable species
- Pachycereus pringlei — the cardón or Mexican giant cactus, a massive branching tree cactus of Baja California and Sonora, often cited as the largest cactus species.
- Pachycereus schottii — the senita cactus, a clumping, many-stemmed columnar species; its monstrose form is the famous totem-pole cactus (see below).
- Pachycereus marginatus — the Mexican fence post cactus, a slender, evenly ribbed column with pale areole margins, widely used as a living fence and landscape plant.
- Pachycereus weberi — a large, tree-like candelabra cactus of southern Mexico.
- Pachycereus pecten-aboriginum — the hairbrush cactus, a big tree cactus named for its bristly fruits.
Species boundaries in this group have shifted over the years, and some plants once placed in related genera such as Lophocereus and Marginatocereus are now treated within Pachycereus. Names in the trade can therefore vary.
Cultivation and hobby notes
Most Pachycereus are straightforward, sun-loving cacti given warmth and sharp drainage. Grow them in a gritty, mostly mineral mix in the brightest position available, water generously during the warm growing season once the soil has dried, and keep them dry and frost-free through winter. They are vigorous and can become heavy, so a stable pot and occasional repotting into fresh, free-draining medium keep young plants growing steadily. See Watering for general technique.
Their eventual size makes the true giants better suited to landscapes in mild, frost-free climates than to a windowsill, but they are slow enough that young plants spend many years as manageable container specimens. Two forms dominate hobby collections:
- The totem-pole cactus, a monstrose, spineless form of Pachycereus schottii with smooth, lumpy, wavy stems and no defined ribs. It is grown purely for its sculptural look and is propagated only vegetatively.
- The Mexican fence post (Pachycereus marginatus), an easy, fast, tidy column popular for hedging and quick vertical accents.
Propagation is by seed for the species and by stem cuttings for named or monstrose forms; large cut sections should be callused in a dry, shaded spot before potting. Slow or choice plants are sometimes grafted to speed growth. Watch for the usual cactus troubles — mealybugs and scale in the ribs, and basal rot from cold, wet conditions.
See also
- Pachycereus pringlei · Pachycereus schottii · Pachycereus marginatus
- Soil and potting mix · Watering · Repotting
- Propagation — seed · Propagation — cuttings · Grafting · Pests and diseases