It's specific name comes from old Greek and means "red spine" for
the colour of its clusters of spines.
It's a barrel type of cactus and stay globular during a long period
before becoming shortly column-shaped.
Description: Demnozas is a large
slowly growing columnar cactus. It stay
globulous during a long period before becoming shortly
column-shaped, 0.5 to 1.5 cm high.
Stem: The plant's diameter ranges from 15 to 30 cm, the stem
colour varies from pale green to dark green
Ribs: 15 to 30, , parallel straight, slightly undulate, broad
basally up to 1 cm tall.
Areoles: Well spaced at first, later confluent. Flower producing
areoles often bears many long bristles and up to 7 cm long spines.
Radial spines: 8 to 10, brownish-red becoming grey, awl shaped
and slightly curved, very different in young and old plants. There is
also a form ("flavispina")
with orange-yellow spines.
Central spines: 1 (But often absent) stouter up to 3 cm long
Flowers: They need to reach a reasonable size in cultivation
before producing their flowers. First flowers appear near the top of the
stem, however, on plants of very unequal age and size, some time on
relatively young plants but also on 30-40 years old specimens! Flowers
zygomorphous (bilaterally symmetrical), of a maximum length of 7.5
cm, reddish to bright scarlet in colour and have white hair on the tube.
Floral tube usually curved and slightly dilatated above the pericarpel,
which bears small appressed scales. The flower open sufficiently widely
so that the stigma and red stamen filaments are visible from outside.
Anther exerted at least 10 mm beyond the tube.
Fruit: Globose, dry at maturity, dehiscent with tuft of short
The spines shape and colour of this species is
D. rhodacantha also changes considerably in the
habit with age and the old
specimen after many years start producing long white bristle.
This white bristled form was previously known with the name of
Denmoza "rhodacantha" and ""erythrocephala" looks very different but are
the same species.
Photo of conspecific taxa, varieties, forms and cultivars of
Scientific name: Denmoza rhodacantha,
(Salm-Dyck) Britton & Rose 1922
Origin: Widespread throughout the mountains of Argentina
(Mendoza to Salta) at 2000- 2800 m of elevation.
Habitat: Eastern slopes and foothils.
Conservation status: Listed in
CITES appendix 2.
Etymology: The name of the genus is an anagram of the north-western
province of Mendoza.
Taxonomy: The genus
Denmoza comprises only one
species allied to Cleistocactus, but it has also
been referred to Echinopsis, Cereus,
Echinocactus and Pilocereus.
The plants described as Pilocereus erythrocephalus
and later transferred to Denmoza
has sometimes, for instance by Backeberg, been considered as another
species of the genus. D. rhodacantha
changes considerably in the habit with age. The description of
refers to young plants having strong spines in areoles. Old plants of
the same species with multiple number of spines and sometimes with thin,
6 cm long bristly spines correspond to the description of
- Echinocactus rhodacanthus
- Echinopsis rhodacantha
- Cleistocactus rhodacanthus
- Cereus rhodacanthus and erythrocephalus
- Pilocereus erythrocephalus,
- Denmoza erythrocephala
It has extraordinary scarlet
zygomorphic, tubular flowers. First flowers appear, however, on
plants of very unequal age and size, some time on relatively young
plants but also on 30-40 years old specimens!
A young specimen.
Older plants have numerous spines but younger plants much fewer. The
spines on young plants are rusty-red to orange in colour, aging to grey
rhodacantha is very slow growing cactus but requires no special
condition in cultivation, need full sun and a very draining soil.