Publication: [Basionym: Notocactus mammulosus f. cristatus P.V.Heath 1995 ]
Description
The typical Parodia mammulosa is a small, usually solitary cactus more or less covered by interlacing spines. It is popular and grown for the large yellow flowers. The crested form can also get very nice making a spectacular specimen. The Parodia mammulosa is among the the most wide-spread of the Parodia species and is very variable in appearance and also the several crested clones can appear quite different.
Stem: Fan-shaped to a height of 5-10 cm and a diameter of up to 30 cm with a depressed, spineless apex. The epidermis is shiny, greysh-green to dark green.
Ribs: Straight, well distinct, with prominent, rounded tubercles with chinlike protrusion.
Areoles: Small or large deeply embedded between the tubercles and set about 5 mm apart.
Radial spines: 8 to 30 slender whitish to brownish, needlelike, usually less than 10 mm long.
Central spines: 0-4 (or more) up to 20 mm long, not easily distinguishable from the radials, usually flattish, thicker, straight and more than twice as long white, yellow to brown with a brown tip, one usually flattened.
Flowers: Pale pink to golden yellow beautifully emphasized by the purplish/red stigma lobes, 4 cm in diameter, with a short tube covered with white wool and brown bristles.
Fruits: Globose, elongating at maturity, thin walled.
Seeds: Bell to helmet shaped, with obvious corky hilum, matte brown.
Origin and Habitat
Garden origin (Nursery produced cultivar)
Cultivation and Propagation
Although regarded as a choice and difficult plant it is not too difficult in a greenhouse, but grows quite slowly. The crests are frequently grafted onto a strong Trichoceres trunks but grow very well on their own roots too.
Soil: Use mineral well permeable mineral soil with little organic matter (peat, humus).
Repotting: Repotting should be done every other year, or when the plant has outgrown its pot.
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: They are moderately cold hardy, an can withstand to light frees down to -5° C or less for very short times, but make sure that they are not exposed to severe freezing temperatures, or they may die. Nevertheless it is good advice never let the night-time temperature fall below 5°C. 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: This plant, like other clonal cultivars, may be only propagated vegetatively by 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.
Notes
The cause of cresting is not fully explained; biologists disagree as to why some plants grow in this unusual form. Some speculate that it is a genetic mutation. Others say it is the result of lightning strike or freeze damage, but whatever the stimulus, the growth point of the stem has switched from a geometric point, to a line, which folds and undulates as the crest expands. Though these crested Parodia are somewhat rare, cresting occurs naturally throughout their range, and can be encountered in many other cactus species.
In the ontogenesis a crest can appear any time, but development of crests on large columnar cactus species (such as the saguaro Carnegia gigantea) in the early stages of ontogenesis is unlikely. On the other hand, small species (such as the saguaro Parodia mammulosa) may crest early already at the cotyledons stage.
Bibliography
Major references and further lectures
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Edward F. Anderson “The Cactus Family” Timber Press, 2001
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Curt Backeberg “Cactus Lexicon” Sterling Publishing Company, Incorporated, 1978
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Hiroshi Hirao “Colour encyclopaedia of cacti” Japan 1979 (Japanese language and script)
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Willy Cullmann, Erich Götz (Dozent Dr.), Gerhard Gröner “The encyclopedia of cacti” Portland, OR: Timber Press, 1986
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David Hunt, Nigel Taylor “The New Cactus Lexicon” DH Books, 2006 ISBN 0953813444, 9780953813445
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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