Origin and Habitat: Serra dos Alegres (near Joao Pinheiro), West Minas Gerais, Brazil.
Altitude range: Discocactus griseusSN|12028]]SN|12028]] is found at an altitude of about 850 meters.
Habitat and ecology: This species grows on fine yellowish sand and among grasses and bushes.

• Discocactus griseus Buining & Bredero
• Discocactus catingicola var. griseus P.J.Braun & Esteves

• Discocactus heptacanthus (Barb.Rodr.) Britton & Rose
• Malacocarpus heptacanthus Barb.Rodr.
• Neodiscocactus heptacanthus (Barb.Rodr.) Y.Itô
• Discocactus boliviensis Backeb.
• Neodiscocactus boliviensis (Backeb.) Y.Itô
• Discocactus cangaensis Diers & Esteves
• Discocactus cephaliaciculosus Buining & Bredero ex P.J.Braun & Esteves
• Discocactus cephaliaciculosus subs. nudicephalus P.J.Braun & Esteves
• Discocactus crassispinus P.J.Braun & Esteves
• Discocactus crassispinus subs. araguaiensis P.J.Braun & Esteves
• Discocactus diersianus Esteves
• Discocactus estevesii Diers & Esteves
• Discocactus flavispinus Buining & Bredero
• Discocactus goianus Diers & Esteves
• Discocactus diersianus subs. goianus (Diers & Esteves) P.J.Braun & Esteves
• Discocactus diersianus var. goianus (Diers & Esteves) P.J.Braun & Esteves
• Discocactus griseus Buining & Bredero
• Discocactus catingicola var. griseus P.J.Braun & Esteves
• Discocactus hartmannii (K.Schum.) Britton & Rose
• Echinocactus hartmannii K.Schum.
• Neodiscocactus hartmannii (K.Schum.) Y.Itô
• Discocactus hartmannii subs. giganteus P.J.Braun & Esteves
• Discocactus hartmannii subs. setosiflorus P.J.Braun & Esteves
• Discocactus heptacanthus subs. melanochlorus (Buining & Bredero) P.J.Braun & Esteves
• Discocactus melanochlorus Buining & Bredero
• Discocactus heptacanthus var. riomortensis P.J.Braun & Esteves
• Discocactus heptacanthus var. semicampaniflorus (Buining & Bredero) P.J.Braun & Esteves
• Discocactus semicampaniflorus Buining & Bredero
• Discocactus lindaianus Diers & Esteves
• Discocactus magnimammus subs. bonitoensis Buining ex J.Theun.
• Discocactus hartmannii var. bonitoensis (Buining & Bredero) P.J.Braun
• Discocactus mamillosus Buining & Bredero
• Discocactus hartmannii var. mamillosus (Buining & Bredero) P.J.Braun
• Discocactus nigrisaetosus Buining & Bredero
• Discocactus catingicola var. nigrisaetosus (Buining & Bredero) P.J.Braun & Esteves
• Discocactus pachythele Buining & Bredero
• Discocactus paranaensis Backeb.
• Discocactus patulifolius Buining & Bredero
• Discocactus hartmannii subs. patulifolius (Buining & Bredero) P.J.Braun & Esteves
• Discocactus hartmannii var. patulifolius (Buining & Bredero) P.J.Braun
• Discocactus piauiensis P.J.Braun & Esteves
• Discocactus prominentigibbus Diers & Esteves
• Discocactus rapirhizus Buining & Bredero
• Discocactus catingicola subs. rapirhizus (Buining & Bredero) P.J.Braun & Esteves
• Discocactus silicicola Buining & Bredero
• Discocactus silvaticus Buining & Bredero
• Discocactus spinosior Buining & Bredero
• Discocactus squamibaccatus Buining & Bredero
• Discocactus squamibaccatus var. longiflorus P.J.Braun & Esteves
• Discocactus subterraneo-prolifer Diers & Esteves

• Discocactus heptacanthus subs. catingicola (Buining & Bredero) N.P.Taylor & Zappi
• Discocactus catingicola Buining & Bredero

• Discocactus heptacanthus subs. magnimammus (Buining & Bredero) N.P.Taylor & Zappi
• Discocactus hartmannii subs. magnimammus (Buining & Bredero) P.J.Braun & Esteves
• Discocactus hartmannii var. magnimammus (Buining & Bredero) P.J.Braun
• Discocactus magnimammus Buining & Bredero

Description: Discocactus griseusSN|12017]]SN|12028]] is a more or less distinct local form of the variable Discocactus heptacanthusSN|12028]]SN|12017]]. It is a small solitary flattened cactus distinguished from the type species for the grey-green colour of the body. However the distinguishing characteristics of Discocactus griseusSN|12017]]SN|12028]], appear to fall within the natural variation of Discocactus heptacanthusSN|12028]]SN|12017]] and it should be synonymized with the latter. Mature individuals possess a small cephalium, a structure formed by trichomes (woolly hairs) from which on warm summer nights emerge the tubular, white, flowers. Its fragrant flowers are pollinated by moths.
Derivation of the specific name: Griseus Latin, Grey, for the grey-green colour of the body.
Stem: Single, flattened spherical, up to 4 cm high (without cephalium), but often taller in cultivation (up to 7 cm), 12-14 cm in diameter, blue-green to grey-green.
Ribs: 9-11 vertical.
Areoles: Oval, to 2.5 cm apart, at first with cream hairs, then bare. Number of areoles per rib is 6-8 on plants with cephalium.
Radial spines: 6-10, ivory to grey, with a light brown/red tip, progressively longer from top to bottom of the areole, of which 3-5 stout up to 2 mm in diameter, one of them (the lowermost) to 25(-35) mm long, bent downwards, two to four of them to 15(-30) mm long, pointing sidewards, the uppermost (if present) are usually shorter (ca. 5 mm), also directed to the sides and upward. All spines are slightly bent to the plant.
Central spine: Absent.
Cephalium: Up to 2 cm high and 2.5-4.5 cm in diameter, with creamy white hairs and small brownish or reddish spine-like bristles along the the margin..
Flowers: About 5.5 cm long and 4.5 cm in diameter, white, naked. The position if the stigma is half-way up the secondary stamens.
Fruits: Brownish-reddish, pinkish-white or white.
Seeds: Black helmet-shaped.

Bibliography: Major references and further lectures
1) Buining, A.F.H. “Die Gattung Discocactus Preiffer.” Venlo, O.J. 1980. page 174
2) Buining & Brederoo in Succulenta Nederlands nr. 54 1975 page 185-190
3) Urs Eggli, Leonard E. Newton “Etymological Dictionary of Succulent Plant Names” Springer Science & Business Media, 29 June 2013

Cultivation and Propagation: Discocactus griseusSN|12028]]SN|12028]] is not the easiest plant to keep happy, especially on year old seedlings are very sensitive to fungal disaeses, 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. Discocactus griseusSN|12028]]SN|12028]] is a species very rich in flowers and seeds.
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.