Description
Astrophytum asterias var. nudum (a.k.a. cv. Ruri Kabuto) has a very characteristic glabrous stem lacking the white tufts of loose hairy scales typical of the common Astrophytum asterias.
Crested form: The crested form (Astrophytum asterias var. nudum f. cristata) - despite to its beauty - is very rare and sought after by collectors, for its unique features remembering of Lophophora williamsii var. cristata. It is a small low growing crested cactus that will slowly forms tangled groups up to 30 cm (or more ) in diameter with age. The plant tends to grow seated in substrate, but in cultivation it is almost always seen grafted on columnar cacti. There are several crested clones mainly selected by Asian growers.
Habit: It is usually solitary unless damaged.
Stem: Green, grey-green to dark olive green, much depressed, fan-shaped mature plants 2-7 cm tall, 5-16 cm broad, smooth completely flake free (without the minuscule tufts of bright white hairy scales).
Ribs: The stem is typically divided by very narrow but distinct vertical grooves into 8 broad ribs. The ribs are very low, almost flat on top, forming triangular sections with no cross-grooves.
Areoles: Round, prominent, 3-12 mm in diameters, forming a line up to the centre of each rib, felted to hairy, white till straw-coloured, then grey. Normally 3 to 10 mm apart.
Spines: Not any.
Flowers: Apical, diurnal, radial, 3-5 cm long, 5-7(-9) cm in diameter opening widely, yellow with orange/red throats.
Blooming season: Spring to summer and each flower lasts for one or two days only.
Origin and Habitat
Garden origin (Nursery produced cultivar)
Cultivation and Propagation
Although regarded as a choice and difficult plant is not too difficult in a greenhouse, but grows quite slowly. It is sometime seen as a grafted plant but grows on its own roots too. Use mineral well permeable mineral soil with little organic matter (peat, humus). Water sparingly from March till October (weekly during summertime, if the weather is sunny enoughand) , with a little fertilizer added. keep perfectly dry in winter at temperatures from 5 to 15 degrees centigrade. (but it is relatively cold resistant and hardy to -7° (-10°)C for short periods) In the rest period no high atmospheric humidity!! They need a good amount of light shade to full sun this help to keep the plants healthy, although slow growth. Be careful: The epidermis of Superkabuto is harder than in the normal asterias and cracks easily if plants are overwatered.
Propagation Grafting.or cuttings. Plants are usually grafted onto column-shaped cacti but proved to be able to produce their own roots if degrafted.
Bibliography
Major references and further lectures
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Edward Anderson “The Cactus family” Timber Press, Incorporated, 2001
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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 R Hunt; Nigel P Taylor; Graham Charles; International Cactaceae Systematics Group. “The New Cactus Lexicon” dh books, 2006
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N. L. Britton, J. N. Rose: “The Cactaceae. Descriptions and Illustrations of Plants of the Cactus Family.” Volume III, The Carnegie Institution of Washington, Washington 1922
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Brian Loflin, Shirley Loflin “Texas Cacti: A Field Guide” Texas A&M University Press, 26/Oct/2009
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Albert Michael Powell, James F. Weedin “Cacti of the Trans-Pecos and Adjacent Areas” Texas Tech University Press, 2004
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Del Weniger “Cacti of Texas and Neighboring States: A Field Guide” University of Texas Press, 1984
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Alfred Richardson “Plants of Deep South Texas: A Field Guide to the Woody and Flowering Species” Texas A&M University Press, 2010
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Jackie M. Poole, William R. Carr, Dana M. Price “Rare Plants of Texas: A Field Guide” Texas A&M University Press, 2007