Publication: Kakteen Sukk. 59(8): 212 (211; figs.). 2008 [Aug 2008] (cf: Kakteen Sukk. 44(5): 105. 1993 nom. inval. basionym not validly published )
Description
Discocactus multicolorispinus is clearly another geographical form of Discocactus placentiformis (Lehm.) Schumann, a species first described in 1826! Discocactus placentiformis is a variable species that comprises several questionable varieties and its taxonomic history has undergone several changes. The differences usually concern the spination, however the colouring, size and density of spines is influenced by the conditions of culture, at lower light levels the spines are less numerous, delicate, while with strong solar radiation the spines are stronger with a darker tint. Minor differences can also be found in the colour of stems, ribs, cephalia and flowers. Discocactus multicolorispinus is distinguishable for the spines mostly amber like, but variable in colouration (multicolored) hence the name.
Stems: Flattened-globular, less than 8 cm tall and about 12 cm in diameter dark green green, with woolly cephalium.
Ribs: About 13. Number of areoles per rib is around 10 on plants with cephalium.
Areoles: Round.
radial spines: 5 to 8 of which the 2(-4) upper ones shorter pointing upwards about 5 mm long. The length of the spines on the sides and downwards is about 1.5 cm. Mostly amber like, but variable in colouration.
Central spines: In some plants one central spine appears, but is usually absent. It is erect, 1,5-2 cm long.
Cephalium: Cream-white.
Flowers: Nocturnal lasting only a single night, and rapidly collapsing into mush the next morning, extremely fragrant, slender funnelform, white arising from the cephalium. The position of the stigma is half-way up the stamens.
Blooming season: Summer, it needs a good exposure to with some sun to bloom, so it’s pretty rare to have blossoms when in cultivation in greenhouses. It is not unusual for this Melocactus to take 7 or more years before it starts blooming, but once it does, it should every year. Grafted plants may flower in 3 years.
Fruit: Club shaped white.
Origin and Habitat
Conselheiro Mata, Barao de Quacuy, and Datas, at the border of the Serra do Espinhaco in Minas Gerais. Brasil.
Altitude range: Around 1000 metres above sea level.
Cultivation and Propagation
Discocactus multicolorispinus is not the easiest plant to keep happy, so it isn’t a plants for beginners, in fact collectors consider the Discocactus to be rarities which requires skilful cultivation. Under glass, it isn’t difficult, but appreciates milder winter temperatures and more generous summer watering than most of the other genera of compact cacti. When grown to maturity, however, it possess an exotic look shared by no other cacti, and it generally attract a lot of attention.
Growing rate: It is slow growing.
Soil: It likes very porous standard cactus mix soil. Prefer a low pH compost, avoid substrata rich in limestone; otherwise growth will stop altogether.
Repotting: They generally resent being repotted and can take a long time to establish.
Fertilization: Feed with a high potassium fertilizer in summer.
Exposition: The plant tolerates bright situations but enjoys filtered sunlight or afternoon shade, inside it needs bright light, and some direct sun. Tends to bronze in strong light, which encourages flowering and heavy spine production.
Waterings: Discocacti are very rot prone when kept on their own roots and though they can’t endure long stretches of total dryness, too much water with cool will rot them, as their weak root systems tend to be inefficient at sucking up water from wet soil.
Hardiness: It is rather difficult to grow and frost tender, it can’t stand cold, or even fairly cool temperatures and should be kept at above 15° C if grown on its own roots (8°C if grafted).
Uses: It is an excellent plant for container growing. It always looks good and stays small.
Pests & diseases: It may be attractive to a variety of pests or diseases:
- Red spiders: Red spiders may be effectively rubbed up by watering the 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.
- Scales: Scales are rarely a problem.
- Rot: Rot it 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.
Propagation: Seeds or 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! .Young seedlings are often grafted on a low stock to keep the plant in a good shape.
Bibliography
Major references and further lectures.
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Cactus and Succulent Journal of Great Britain, Volume 44 Cactus and Succulent Society of Great Britain, 1982
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Kakteen und andere Sukkulenten 1979 nr. 3 page 59
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BRAUN, P.J.; BREDEROO, A. 1981. “D. multicolorispinus Braun et Brederoo.” Kakteen und andere Sukkulenten 16(4): 76-78.
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