These are not as common in the trade as some of the others, but well worth buying if you happen to see one. The Stenocactus genus includes globular cactus with a distinctive wavy rib pattern, instead of straight ribs. Native to Mexico, the original genus included only about 10 species, although Hertrichocereus and Echinofossulocactus are now included in this group, expanding the number of species to about 30.
It's not uncommon to see them identified only as "Stenocactus" when they're offered for sale. Besides their distinctive wavy ribs, these cacti also feature stiff and short spines. Younger plants lack the distinctive wavy ribs and have tubercules. These will develop into the typical ribs when the plant is older.
Light: Stenocactus like bright sunlight and thrive in full sun and strong light.
Water: Throughout the growing season (spring and summer) let the potting soil almost completely dry out between waterings, then water thoroughly. In winter, cut back watering.
Soil: A rich, fast-draining cactus mix is ideal.
Fertilizer: During the growing season, fertilize with a cacti fertilizer mix. Suspend feeding during the dormant winter period.
Stenocactus propagate easily from seed. The seeds readily germinate. Seeds are contained in green seedpods. The plants are not able to fertilize themselves, so if you're not getting seedpods from a single specimen or one that is flowering alone, wait until you have several plants that are flowering simultaneously.
Once you have a seedpod, sow the seeds in a cactus seedling starter mix and keep them barely moist until they sprout.
Repot as needed, preferably during the warm season. To repot cacti, make sure the soil is dry before repotting, then gently remove the pot. Knock away the old soil from the roots, making sure to remove any rotted or dead roots in the process.
Treat any cuts with a fungicide. Place the plant in its new pot and backfill with potting soil, spreading the roots out as you repot. Leave the plant dry for a week or so, then begin to water lightly to reduce the risk of root rot.
All the Stenocactus share the same "brainlike" wavy ribs that characterize the plant. Most of the species are small, globular plants that remain less than 4 inches in diameter. Also, unlike many other cacti species, many Stenocactus are frequently solitary or single plants and do not put out offsets. Although these are not common, here are few of the more popular Stenocactus:
- S. crispatus. This plant features long spines in a profusion, covering its ribs. It flowers with white or pink flowers with a darker stripe down the mid-petal. This plant does eventually produce offsets.
- S. phyllacanthus. This plant produces smaller yellow flowers. It's a solitary plant with stiff spines that does not produce offsets.
- S. coptonogonus. A remarkable specimen with straight ribs and stiff, short spines. The white flowers emerge from the center of the crown and feature lavender stripes on the midstripe.
Their water and light requirements are fairly typical for many cacti species, including a cooling period in the winter to promote better blooming. Watering should be done carefully, allowing the plant to almost dry out between waterings. It's imperative that the cactus is not exposed to prolonged dampness and sitting water. Never let your cactus sit in a dish of water. For the best viewing, instead of propagating your offsets, let the plant for a large cluster. Lastly, make sure to fertilize during the growing season for the best results.