Description: The Copiapoa tenuissima
is a single headed or slowly clumping,
usually at or slightly below soil level.
Stems: Up to 5 cm in diameter, flattened to spherical,
dull-green, dark olive green, to almost purplish-black. The stem is
tubercled rather than ribbed stem and the slightly felted apex can be
regarded as persistent juvenile characters, which can be explained by
the need for the plant to multiply as early as possible, before they
fall victim to the Guanacos.
Roots: Large tuberose connected to the stem by
long slender neck. Seedlings naturally produce the huge tap root,
starting from germination, i.e. before the plant stem becomes mature.
Ribs: 13-16 spiralling, 3-4 mm tall.
Areoles: White abundantly woolly.
Radial spines: Very thin (almost hairy), acicular, usually
straight 8-14, 3-6 mm long, yellowish to blackish.
Central spines: 0-1 (-2) 4-10 mm long.
Flowers: Pretty, yellow diurnal, up to 2.5 cm long. Tepals up to
15 mm long 5-7 mm wide. Ovary with pubescent scales, floral tube 4-7 mm
long. The flowers are supposedly to be sweet scented. (The hairy ovary
and fruit are a link with Ritter's Pilocopiapoa solaris)
Blooming season: Spring and summer. In
cultivation in the C. tenuissima are able to flower from immature stems
at an early age (c. 2 years from germination) and set viable seed.
Fruit: Globose, green to maroon unusual for the genus by being
woolly, a primitive characteristic.