Origin and Habitat: North of Diamantina in Minas Gerais, Brasil, also further west near Vila Sopa and Barrao de Quacuy and adjacent areas.
Altitude: Altitude of 500 to 1000(-1350) metres above sea level.
Habitat: It grows in rocky soil, among rocks, grasses, often with Bromeliaceae or under low growing shrubs.

• Discocactus placentiformis (Lehm.) K.Schum.
• Cactus placentiformis Lehm.
• Echinocactus placentiformis (Lehm.) K.Schum.

• Discocactus placentiformis (Lehm.) K.Schum.
• Cactus placentiformis Lehm.
• Echinocactus placentiformis (Lehm.) K.Schum.
• Discocactus alteolens Lem. ex A.Dietr.
• Cactus alteolens (Lem.) Kuntze
• Discocactus alteolens Schum.
• Discocactus placentiformis subs. alteolens (Lem.) P.J.Braun & Esteves
• Discocactus placentiformis var. alteolens (Lem.) P.J.Braun & Esteves
• Echinocactus alteolens (Lem. ex A.Dietr.) K.Schum.
• Discocactus besleri F.A.C.Weber
• Discocactus crystallophilus Diers & Esteves
• Discocactus insignis Pfeiff.
• Discocactus latispinus Buining ex Bredero ex J.Theun.
• Discocactus linkii Pfeiff.
• Discocactus multicolorispinus P.J.Braun & Bredero
• Discocactus placentiformis subs. multicolorispinus P.J.Braun & Esteves
• Discocactus placentiformis var. minor-horridulus n.n.
• Discocactus pseudolatispinus Diers & Esteves
• Discocactus latispinus subs. pseudolatispinus (Diers & Esteves) P.J.Braun & Esteves
• Discocactus pugionacanthus Buining & Bredero ex J.Theun.
• Discocactus placentiformis subs. pugionacanthus (Buining & Bredero) P.J.Braun & Esteves
• Discocactus placentiformis var. pugionacanthus (Buining & Bredero) P.J.Braun & Esteves
• Discocactus pulvinicapitatus Buining & Bredero
• Discocactus latispinus subs. pulvinicapitatus (Buining & Bredero) P.J.Braun & Esteves
• Discocactus tricornis Monv. ex Pfeiff.
• Echinocactus tricornis Monv. ex A.Dietr.

Description: Discocactus placentiformisSN|1430]]SN|1430]] is a small flattish globular cactus from Brazil that flowers on warm summer nights. It is one of the most widely distributed and variable species with several unnecessary subspecies described.
Stem: Low, flattened-globular, less than 10 cm tall (without cephalium about 3,5-8 cm), (6)-12-14(-22) cm in diameter light, dark or bluish green, with woolly cephalium.
Ribs: mostly 10-16 low to acute up to 1,5 cm high, not or only slightly tuberculate, distinctly enlarged at the areoles and without acute sinuses between adjacent areoles on the same rib.
Areoles: Round to oval 5-8 on each rib on plants with cephalium.
Cephalium: 3,5 cm tall, 4-6 cm in diameter, with cream-white, greyish-white or greyish-brown wool and black bristles 1,5-2,5 cm long.
Radial spines: 3-5(-9) conspicuous, pale gray, reddish, brown or blackish with a darker tip , becoming grey with age, 1-3 cm long and up to 2 mm thick, often flattened, clawlike, slightly recurved backwards to the plant, lateral spines longer and pointing downwards.
Central spine: In some plants one central spine appears, but is usually absent. It is erect, 1,5-2 cm long.
Flowers: Nocturnal lasting only a single night, and rapidly collapsing into mush the next morning, extremely fragrant, slender funnelform, up to to 7,5 cm long, white arising from the cephalium.
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.
Fruit: Club shaped white or cream sometime with a pink tip, up to 3 cm long and 0,8 cm in diameter containing a few black seeds.

Bibliography: Major references and further lectures
1) Edward Anderson “The Cactus family” Timber Press, Incorporated, 2001
2) 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
3) David R Hunt; Nigel P Taylor; Graham Charles; International Cactaceae Systematics Group. "The New Cactus Lexicon" dh books, 2006
4) N. L. Britton, J. N. Rose “The Cactaceae. Descriptions and Illustrations of Plants of the Cactus Family.” Volume 4, The Carnegie Institution of Washington, Washington 1923
4) Urs Eggli, Leonard E. Newton “Etymological Dictionary of Succulent Plant Names” Birkhäuser 2004.
5) Clive Innes “Complete Handbook of Cacti and Succulents” Van Nostrand Reinhold Company, 01/Dec/1981
6) John Pilbeam “Cacti for the Connoisseur: A Guide for Growers & Collectors” Timber Press, 01/Jul/1987
7) Engler, Prantl: “Natürlichen Pflanzenfamilien” Volume 3, 6a, 1894, page. 190.
8) Pierre Josef Braun, Eddie Esteves Pereira “Aggregationen in Discocactus Pfeiffer (Cactaceae).” In: Kakteen und andere Sukkulenten. Volume 44, 1993, page. 62, page. 103, page. 112.

Cultivation and Propagation: Discocactus placentiformis 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.