Xerophyte

Habit

It is usually solitary or slowly branching through basal shoots.

Description

Echinopsis thionanthaSN|5]]SN|5]] (best known in cultivation as Acanthocalycium thionanthumSN|80]]SN|80]]) is a highly variable taxon with several forms. The specific name "thionantha" was originally applied to the yellow flowering form, but now comprises plant of variable colour of flowers and spines sizes. There are a number of varieties, but not all are universally recognized.

Flowers

Bell-shaped, 5 cm long or less on lateral areoles, and the segments of the perianth are sulphur or lemon-yellow (but also white, orange or red), They have very hairy buds. The floral tubes have brown-white hairs/bristles and dark spine-tipped scales.

Spines

5 to 10 radial spines and 1 to 4 central spines, they are all more or less of the same length in a given plant (5-30 mm), but this species appears to be very variable regarding the length colour and number of spines in different populations. They are usually black or light brown at first, becoming grey or whitish-yellow as they age.

Ribs

About 9-15.

Stem

Spherical, over time it becomes slightly cylindrical, growing to a height of 12 cm or more, and a diameter of 6 to 10 cm. The epidermis is green to dark blue grey, and become a clear powdery-grey in the older part of the stem (like some Copiapoa)

Areoles

At the apex of tubercles, at first are covered with yellowish-brown felt. The flower part of the areola is elongated, while the upper part curves around the sides of the rib, more or less in the shape of a small shield. As the tubercles widen in the course of growth, the areoles become elliptical and almost glabrous.