Cleistocactus strausii

Cleistocactus strausii
Scientific classification
Kingdom:	Plantae
(unranked):	Angiosperms
(unranked):	Eudicots
(unranked):	Core eudicots
Order:	Caryophyllales
Family:	Cactaceae
Genus:	Cleistocactus
Species:	C. strausii
Binomial name
Cleistocactus strausii

Cleistocactus strausii (silver torch or wooly torch) is a perennial cactus of the family Cactaceae. It is native to high mountain regions of Bolivia and Argentina, above 3,000 m (9,843 ft).

Its slender, erect, grey-green columns can reach a height of 3 m (10 ft), but are only about 6 cm (2.5 in) across. The columns are formed from around 25 ribs and are densely covered with areoles, supporting four yellow-brown spines up to 4 cm (2 in) long and 20 shorter white radials.

The cactus prefers free draining soils, strong sunlight, but not high temperatures — in fact it can withstand hard frosts down to -10°C. In its natural habitat it receives plenty of water during the summer, but almost none over the winter. In cultivation, watering too much in winter often leads to root rot.

Older cactuses, over 45 cm (18 in) tall, produce deep red, burgundy, flowers in late summer. The 6 cm (3 in) long cylindrical flowers protrude horizontally from the columns. In common with other cacti in the genus Cleistocactus, the flowers hardly open, with only the style and stamens protruding. Cultivated plants often flower freely. In the United Kingdom, this plant is usually grown under glass, and has gained the Royal Horticultural Society's Award of Garden Merit.

When mature, the silver torch cactus produces red flowers extending horizontally from the main columns.

Flowers by silver torch cactus

External links

• close up picture of flowers
• desert-tropicals.com
• University of Connecticut Ecology department
• Bihrmann's caudiciforms