This is one of the most distinctive Rebutias, and is very hard to obtain.  The flowers are yellow with a  lovely  hue of custard-powder, and are relatively large for so tiny a plant ... ... but is relatively hard to grow.

Family: Cactaceae (Cactus Family)

Scientific name:  Rebutia gonjianii Kiesling,
Bol. Soc. Argent. Bot., p. 132, 1963

Origin:  North-east Argentina (Jujuy, Salta), south east Bolivia

Conservation status: Listed in CITES appendix 2.

Synonyms:

• Rebutia einsteinii var. gonjianii (Kiesling) Donald,
  Ashingtonia, 1 : 83, 1974
• Rebutia Gonjiana, B. Gonjian[gonchian]
• Lobivia einsteinii var. gonjianii (Kiesling), Rausch,
  Lobivia 85, 1986
• Cylindrorebutia gonjianii
• Digitorebutia gonjianii
• Lobivia einsteinii var. gonjianii (Kiesling) Rausch 1985
• Pygmaeolobivia lanata n. p. Rausch
• Mediolobivia einsteinii var. gonjianii
• Mediolobivia gonjianii
• Rebutia einsteinii subsp. gonjianii (Kiesling) Hjertson 2003
• Lobivia euanthema
• Acantholobivia euanthema

Rebutia gonjianii
This is one of the most distinctive Rebutias, and is very hard to obtain.

Description: R. gonjianii is a small, clumping cactus.  It can become quite tall, and branch in the manner of a miniature saguaro.  This species is often seen lumped with R. einsteinii.
Stems: Cylindrical, dark brownish-green coloured, but green in the new growth, and only about as thick as a pencil (1-1,2 cm in diameter).  It would appear that in cultivation these plants grow larger, elongate and cluster more vigorously than in habitat.
Root: Thick, fleshy taproot.
Spines: Tiny
Flowers: Large yellow, with a tinge of orange or brownish-yellow.
Blooming Season: Blooms profusely in spring.

Cultivation: This species is probably the most difficult Rebutia to growon its own (tuberous) roots, and it is often grown grafted.   It tends to rot if too wet, and is best kept in a somewhat sheltered location.  Careful waterings helps to keep the plant compact.  Grow it in a very open mineral mix, (lots of pumice).   Keep dry in winter.   Hardy to -4°C for a short period.  Rebutias grow in nature at high altitudes, and do not thrive well at high temperatures in cultivation.  They will often go dormant in mid-summer and resume growth again when the weather cools in late August.  They can tolerate amazingly low temperatures for long periods of time.  All species can take frost, even when not bone dry. It is generally accepted that plants kept at too high a temperature, or watered too much during the winter rest period, will not bloom the following year.  Give them an airy spot, and ensure good drainage. It is better that they be repotted regularly.  Pots should be only slightly larger than the plant and root system.
The roots can break during repotting, and it is best to leave the compost dry for a while after repotting, to avoid rot.  Repotting will increase the number and size of stems, and will increase the number of flowers produced. Repot yearly until reaching about 3 cm in size, then every two or three years will suffice.  Repotting is best done at the end of winter, but can be done at other times, too.  All plants, especially the young ones, are susceptible to red spider mites.

Propagation:  By seeds or offsets (If available).  The stems of larger grafted specimens can be rooted, but grow quite slowly.  It makes sense to keep some stock plants for future propagation, or to replace the eventaul plant that rots or dies.

Rebutia gonjianii is one of the best rebutias.   The flowers are yellow with a  lovely  hue of custard-powder, and are relatively large for so tiny a plant ... ... but is relatively hard to grow.