With its square, jointed, succulent stems, this fascinating pelargonium
could easily mislead the casual observer into mistaking it for a
member of the Euphorbia family.
Pelargonium tetragonum is a plant adapted to grow in
dry habitats (xerophyte). It branches from the base and if supported
by other vegetation, will reach a height of 2 m. The plant tends
to sprawl, but can be successfully grown as a pot specimen. Pelargonium
tetragonum is distinguished by its almost leafless, three- to
four-angled, jointed and succulent stems. When present, the leaves
are fleshy, palm-shaped and sometimes have red zonal markings. The
very attractive cream to pink flowers occur in pairs on the flower
stem. Each flower has four petals, with the upper two significantly
larger than the lower pair. The large upper petals are streaked
with red. The flowering time is from September to December.
Pelargonium tetragonum is only found in dry habitats
within a strip parallel to, but inland from the South African south
coast, extending from Worcester to Grahamstown. This distribution
thus extends from the winter rainfall region in the west to the
summer rainfall area in the east.
Derivation of name
The specific name, tetragonum, is derived from the Greek
words tetra (four) and gonia- (angled) and refers
to the characteristic square-shaped stem. The genus Pelargonium
consists of over 200 species, of which some 80% occur in southern
Africa. Of these, approximately 80% are found in the southwestern
Cape. The misnomer 'geranium' refers to the hybrids derived
from south African pelargoniums, and now extensively grown throughout
Unlike many other pelargoniums, this species does not produce aromatic
oils. However, the attractive flower and unusual growth form make
this a worthwhile addition to any pelargonium collection.
Growing Pelargonium tetragonum
P. tetragonum favours arid, rocky habitats, and will rot
if over-watered. It is therefore best suited to well-drained and
dry situations in the garden, and thus an excellent choice for a
water-wise garden. It is easily propagated from stem cuttings using
river sand as the rooting medium. Dipping the cuttings in a rooting
hormone will increase the chances of success. Keep the river sand
damp during the rooting process, but do not over-water. (Liesl van
der Walt, Kirstenbosch pers. comm.)
Van der Walt, J.J.A. 1977. Pelargoniums of southern Africa.
Purnell, Cape Town.
Dr. Andy Moore
Kirstenbosch National Botanical Garden