Publication: = cristata
Description
Ariocarpus kotschoubeyanus (a.k.a. Star Rock) is a well known flat geophytic cactus that produce small star-shaped rosettes. They in most cases don’t reach more than only a few centimetres above the ground. The crested form Ariocarpus kotschoubeyanus f. cristatus - despite to its beauty - is still very rare and sought after by collectors, for its unique features.
Root: Has a large tap root below the surface of the compost.
Stem: Fan shaped, flattened on top, depressed centrally.
Tubercles: The tubercles are deltoid dark olive green with no spines and lie flat on the soil surface. They are more long than wide, closely packed and divergent, sharply angled apically.
Areoles: The tubercles forms a central longitudinal areolar groove extending to the tips on the adaxial surfaces of the tubercles, woolly, 1-3 mm wide, 5-10 mm long.
Flowers: These plants have a woolly crown, from which emerge bright pink-violet flowers up to 2,5-5 cm, 2 times wider than long when fully expanded. Flowers are diurnal and last for 3 to 4 days.
Blooming time: Mid-September onwards.
Origin and Habitat
Garden origin (Nursery produced cultivar)
Cultivation and Propagation
It is not too difficult in a greenhouse, although grows quite slowly. It is usually seen as a grafted plant but can grow on its own roots too.
Soil: Use a mineral well permeable soil with little organic matter (peat, humus).
Exposure: They need a good amount of light shade to full sun this help to keep the plants healthy, although slow growth.
Watering: Water sparingly from March till October (weekly during summertime, if the weather is sunny enough), with a little fertilizer added. Less or no water during cold winter months, or when night temperatures remain below 10° to prevent root loss. It is sensitive to overwatering (rot prone).
Fertilization: Feeding may not be necessary at all if the compost is fresh then, feed in summer only if the plant hasn’t been repotted recently. Do not feed the plants from September onwards as this can cause lush growth which can be fatal during the darker cold months.
Hardiness: Keep perfectly dry in winter at temperatures from 5 to 15 degrees centigrade. (but it is relatively cold resistant and hardy to -5° C, or possibly colder for short periods) In the rest period no high atmospheric humidity!! (Temperature Zone: USDA 9-11)
Crested growth: Unlike ‘monstrose’ varieties of plants, where the variation from normal growth is due to genetic mutation, crested growth can occur on normal plants. Sometimes it’s due to variances in light intensity, or damage, but generally the causes are unknown. A crested plant may have some areas growing normally, and a cresting plant that looks like a brain, may revert to normal growth for no apparent reason. If you have any of the crested part left you need to remove the normal growth and leave the crested part behind this will need to be done regularly.
Propagation: Grafting or cuttings. Plants are usually grafted onto column-shaped cacti but proved to be able to produce their own roots if degrafted. Cuttings will take root in a minimum temperature of 20° C (but better in hot weather). Cuttings of healthy shoots can be taken in the spring and summer. Cut the stem with a sharp, sterile knife, leave the cutting in a warm, dry place for a week or weeks (depending on how thick the cutting is) until a callus forms over the wound. Once the callus forms, the cutting may be inserted in a container filled with firmed cactus potting mix topped with a surface layer of coarse grit. They should be placed in the coarse grit only; this prevents the cut end from becoming too wet and allows the roots to penetrate the rich compost underneath. The cuttings should root in 2 to 6 weeks. Large crested piece must be placed on the soil surface without burying the plant base down in the soil.
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
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Edward F. Anderson “The Cactus Family” Timber Press, 2001
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Nathaniel Lord Britton, Joseph Nelson Rose “Cactaceae: Descriptions and Illustrations of Plants of the Cactus Family” Volume 3, 1922
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