Mammillaria marksiana is a beautiful, yellow, spring-flowering cactus.
 

Description: Plants solitary at first, later forming clumps.
Stem: Flattened globose, normally light green, becoming yellowish in bright light.  In the wild it can grow up to 6-10 cm high, 5-12 cm in diameter, however in cultivation it can double in size.  Milky sap is present.
Tubercle arrangement: With (usually) eight right-winding and 13 left-winding visible contact parastichies.
Tubercle: Pyramidal, weakly four-sided.
Axil: With lots of snow-white wool, particularly in the blooming area.
Spines: Thin, needle-like, golden yellow to brown, difficult to distinguish as centrals and radials, very variable in number, even within the areoles of the same plant, generally 3 to 8 mm long, depending on age and origin, younger plants have more spines (7-13), older ones have fewer ones (2-5)
Flower: Diurnal, bright greenish yellow, 15 mm long and in diameter. The flowers form in a ring pattern on the previous year’s growth.
Blooming season: Late winter to early spring.
Fruit: Club shaped, greenish or  purplish red, up to 20 mm long, ripening in summer.
Seed: Small, brown.

Scientific name: Mammillaria marksiana Krainz,
 
First description: Sukkulentenk. 2: 21 (1948)

Origin:  Southern Sonora, Durango and Sinaloa, Mexico. Altitude 400 - 2.000 m.

Habitat: This species is quite rare in nature, and generally grows under the protection of nursery plants.

Conservation status: Listed in CITES appendix 2.

Common Names include: Cabeza de Viejo

Synonyms:  

• Neomammillaria marksiana

Cultivation: An easy and easily flowering species, but not a fast grower, that may make large clumps given the best conditions.  Some plants will offset, and moderately large-sized clumps can be produced in a few years.
Water regularly in summer, but do not over-water (rot prone). It shouldn't be watered from above, as it would ruin the fine wool.  Use a pot with good drainage and a very porous potting media, and keep dry in winter. Feed with a high potassium fertilizer in summer. Avoid frost.  Reputedly sensitive to low temperatures, but less so if kept on the dry side prior to, and during, cold weather. Outside full sun or afternoon shade, inside it needs bright light, and some direct sun. Tends to get yellowish in strong light, which encourages flowering and heavy wool and spine production.
 

Propagation: Division, direct sow after last frost.