is one of a number
species which are presently being tested for their
suitability to be grown as Green Roof
plants in the Durban region that have initially shown good results.
occur naturally within a radius of 50 km of the Durban
plants that I am growing were found growing in full sun and partial
in the dry portions of north facing cliffs inland of Durban overlooking
A small spreading
succulent with a tuberous root system. The cultivar being grown is a
much smaller less vigourous growning plant than the cultivar commonly
found in cultivation for landscape purposes. They reproduce naturally
seed which germinates readily.
Delosperma tradescantioides are being grown primarily for their neat growth
habit and attractive
Delosperma tradescantioides can survive
periods of drought.
Disease and pest resistance
To date I have
not seen any pests on the plants neither have I noticed any
Suitability as Green Roof plants
plants are valuable in plantings that are going to get the very minimum
or no water in winter as well in combinations with other plants that do
not have a
very vigorous nature. Delosperma tradescantioides multiplies freely from seed.
Biodiversity value in the Green
large numbers of insects in particular bees and small butterlies.
Cautions and precautions in the Green Roof
must be taken to ensure good drainage.
Drought responses of diurnal gas exchange, malic acid accumulation and
water status in Delosperma tradescantioides. When well-watered, this
species exhibited Crassulacean acid
metabolism (CAM)-cycling, but its carbon fixation pattem
changed during the development of drought, shifting to either low-level
CAM or to CAM-idling. The rate and pattem of this change depended on
environmental conditions, duration of water stress and leaf age. At the
onset of drought, diurnal malate fluctuation increased, but was
strongly depressed (by ca 70%) as drought continued, and when leaf
water content and water potential were low (ca 35 and 50% of the
initial levels, respectively). When rewatered, rates of growth and
photosynthesis, gas exchange and water status recovered fully to
pre-stressed values within two days. Whole-shoot carbon uptake rates
suggested that leaf growth had continued unabated during a short-term (
one week) drought. This emphasises that CAM-idling allows the
maintenance of active metabolism with negligible gas exchange when soil
water is limiting. It is possible that old or senescent leaves may
provide water for the expansion of developing leaves during initial
periods of drought. Regardless of the water regime and environmental
conditions, leaf nocturnal malate accumulation and water content were
positively correlated and increased with leaf age. Thus the gradual
loss of water from older mature leaves may induce CAM-idling, which
reduces water loss. An important ecological consequence of this
combination of CAM modes is the potential to switch rapidly between
fast growth via C3 gas exchanges when well-watered to
water-conserving CAM-idling during drought.