Xerophyte

Seeds

Typical of the genus, winged, with a strongly flattened aril; uneven on its periphery.

Description

It is a geophyte cactus, with strong underground tap-roots and deciduous branches.

Roots

Strong, napiform, cream-coloured, up to 15 (or more) cm long.

Note

In the wild during severe droughts, the aerial green shoots die back to the underground rootstock. Once rains return, the rootstock produces new green shoots that grow upward until they reach the soil surface. Similarly in cultivation - when top growth is pruned, the plants produce new green stems bearing terminal flowers that open in the late spring or early summer. In any case old Pterocactus branches easily detach spontaneously at the smallest collision. They are nearly deciduous!!! Sometimes a very fragile corky necrotic brown zone forms at the branches' base, helping the shoots to break up at the point of union of root and shoot systems. This helps the plant to naturally produce new floriferous stems.

Flowers

Diurnal, rotate, yellow to dirty-yellow, up to 3 cm in diameter, growing apically at the tip of new stems without a clear floral tube distinguishable.

Blooming Season

Summer.

Stem

The thin cylindrical segment usually arises basally from the root-stock (or rarely joined). Stems are green to brown, 3-10 cm long and 0,5-1 cm in diameter.

Radial Spines

10-20

Fruits

Dry and larger than the stem itself, dehiscing transversally in the upper part, opening up like a cap and setting the seed free.

Areoles

Very woolly, without (or with very few) glochids.