Publication: Cactaceae Consensus Init. 3: 6. 1997
Description
Rebutia steinbachii subs. verticillacantha best known as Sulcorebutia verticillacantha is one of the innumerable local form of the very variable Rebutia steinbachii (= Sulcorebutia steinbachii) with 13-21 spiraling ribs, no central spines, and 12-14 pectinated radials. Rings of light purple flowers with a contrasting yellow-orange throat brighten up the plant in spring. In its habitat it is a very variable species.
Note: Rebutia steinbachii subs. verticillacantha is apparently a neotenic variety of the species in which juvenile spination is retained throughout the life of the plant, while many of the other varieties are dimorphic (short spined juvenile forms transform at maturity to strongly spined forms).
Habit: It is a clumping plant growing flat to the ground and readily forming, especially in cultivation, clumps of many heads from the base.
Roots: Non-succulent, fibrous, or more or less thickened and carrot-like.
Stem: Single heads 25–35 mm wide, and up to 35 mm tall, globular, flattened and somehow apically depressed, grey-green to dark olive green sometime tinged red, not completely hidden under the covering of spines.
Ribs: About 17, spiralling, poorly distinguished, forming oblong rhomboid tubercles with well-defined grooves.
Areoles: White or yellowish, long, narrow 3-6 long, 1,5 mm large.
Central spines: Absent.
Radial spiens: (6-)8-12(-14) tiny, thin, pectinate pointing sidewards and downwards up to 5 mm in length. Creamy-white, yellowish or amber, brow at the base. These spines don’t obscure the stem but form a nice spiralling pattern on the stem..
Flowers: Typically yellow with orange petals tip, or light purple with a contrasting yellow-orange troat, but also pure yellow, orange, red or violet or bicoloured, numerous in a ring at the base of the plant.
Blooming season: Spring (April - May) and remain open for up to five days.
Origin and Habitat
Arque and adjacent areas, Cochabamba department, Bolivia.
Altitude: 2900-3900 metres above sea level.
Habitat: It grows on hill sides on rocky outcrop.
Cultivation and Propagation
Sulcorebutias are summer grower species easy to cultivate, more cold tolerant than most. These mountainous plants have thick taproots and are susceptible to overwatering. They requires also an appropriate air circulation and are sometime grafted to avoid root problems.
Growth rate: It is a relatively rapidly growing and easily flowering species that will make clumps given the best conditions.
Soils: It likes very coarse mineral cactus mix soil, but can become too elongated if compost is too rich.
Repotting: Use pot with good drainage.
Watering: Water moderately from Spring to Autumn, but do not overwater (Rot prone), it must be strictly kept dry throughout the winter quiescent period since it is very sensitive to any moisture excesses keep dry in winter.
Fertilization: Feed with a high potassium fertilizer in summer.
Hardiness: They need to be kept in a cool place during winter rest and are somewhat resistant to frost if kept on the dry side prior to, and during, cold weather (due to the altitude they are hardy to -7 C ° C, or less for short periods). The cold is important for the flowers, as well as for their health. Without this cool winter period, they normally won’t get any buds.
Exposition: Requires full sun or light shade and careful watering to keep plant compact with strong coloured spines. Tends to bronze in strong light, which encourages flowering and heavy spine production. Light shadow my be useful in the hottest summer days.
Uses: It is an excellent plant for container growing. It always looks good and stays small. It look fine in a cold greenhouse and frame or outdoor in a rockery.
Pests & diseases: It may be attractive to a variety of insects, but plants in good condition should be nearly pest-free, particularly if they are grown in a mineral potting-mix, with good exposure and ventilation. Nonetheless, there are several pests to watch for:
- Red spiders: Red spiders may be effectively rubbed up by watering the infested plants from above.
- Mealy bugs: Mealy bugs occasionally develop aerial into the new growth among the wool with disfiguring results, but the worst types develop underground on the roots and are invisible except by their effects.
- Sciara Flies: Sciara flies are one of the major problems for seedlings. It is a good practice to mulch your seedlings with a layer of grit, which will strongly discourage the flies.
- Scales: Scales are rarely a problem.
It is wise to treat your whole collection with a systemic insecticide twice a year in spring and autumn.
- Rot: Rot is only a minor problem with cacti if the plants are watered and “aired” correctly. If they are not, fungicides won’t help all that much. To prevent rottenness it is also advisable to surround its root neck by very rough sand or grit, this help a fast water drainage.
Propagation: Seed, cutting, grafting. Seeds germinate in 7-14 days at 21-27° C in spring, remove gradually the glass cover as soon the plants will be well rooted (ca 1-2 weeks) and keep ventilated, no full sun for young plants!
Bibliography
Major references and further lectures
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James Cullen, Sabina G. Knees, H. Suzanne Cubey “The European Garden Flora Flowering Plants: A Manual for the Identification of Plants Cultivated in Europe, Both Out-of-Doors and Under Glass” Cambridge University Press, 11/Aug./2011
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David Hunt, Nigel Taylor “The New Cactus Lexicon” DH Books, 2006 ISBN 0953813444, 9780953813445
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Edward F. Anderson “The Cactus Family” Timber Press, 2001
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John Pilbeam “Sulcorebutia and Weingartia: A Collector’s Guide” Timber Press, 1985
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Cyril Marsden, Herbert Spencer Jackson “Rebutia, Including Aylostera and Sulcorebutia” Macmillan, 1968
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