| Asparagus
densiflorus occur naturally in the greater
Durban region in particular
interest for
use in the establishment of green roofs is the fact that they are often
found
growing
naturally in full sun on inhospitable rocky calcite outcrops on the
seashore
along the Bluff and Isipingo slopes experiencing the full effects of
the salt
laden maritime environment. Here they are often found growing fully
exposed to
the elements at times in locations that are practically devoid of all
soil.
Growth habit
These
plants are medium to low growing evergreen clump forming that easily
reproduce
themselves from seed.
Decorative value
These plants
are most decorative having light glossy green compound leaves and a
fairly neat
growth habit, they produce a profusion of small white flowers in mid to
late summer,
Under stress conditions they can become tatty and untidy.
Drought resistance
These plants
have a very extensive root system with large fleshy grape like tubers
on their
root ends where they are able to store very large amounts of water.
These
plants are able to easily withstand very harsh and dry conditions
provided that
they periodically get a good rain shower to replenish their water
reserves.
Disease and pest resistance
I have not
experienced diseases attacking these plants, however they are often
attacked by
chewing insects and leaf miners both of which appear to do no lasting
damage to
the health of the plant.
Suitability as Green Roof plants
Although
they are fairly slow growing which has not give us enough time to
evaluate them
under out test conditions, due to their well know natural
characteristics it is
hard to believe that these plants will not make very suitable green
roof plants.
Biodiversity value in the Green
Roof landscape
Large
numbers of pollinating insects in particular honey bees are drawn to
the plants
when they are in flower. Birds eat the red berries that are produced in
profusion
Cautions and precautions in the Green Roof
application
None that I
am aware of at the moment
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