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GENERAL
Origin
:
sub-tropical,
tropical
Vigour
:
very slow-
growing
Humidity
:
semi-humid, very
humid
Propagation :
division
Maintenance :
moderate
CONDITIONS
Urban climate :
vulnerable
Dessication :
vulnerable
Stagnant water :
resistant
Salinity/ppm :
moderate (1800
ppm)
Hardiness
:
+3°C
SHAPE
Type
:
ferns, aquatic
Height
:
0.01 m-0.05 m
Spread
:
0.1 m-0.2 m
Foliage
:
evergreen
Floating Ferns are tender aquatic perennials with light-green fronds. The short rhizomes creep
beneath the surface, while the round foliage unfolds lengthwise on top. Concave, evergreen lea-
ves show a prominent midrib and measure about 1 cm in diameter. Stiff hairs build a kind of
cage that encloses an air bubble repelling water from the surface. In this way, the plant floats
on standing water or along banks of slow-flowing streams. Unlike its terrestrial relatives, the
Floating Fern grows its sori (containing the spores) on the upper surface. They are released from
sporocarps that are branched like a corymb. Slowly but steadily growing, the plants form dense
mats that blanket the water densely about 5 cm thick. They originate from tropical America, but
easily naturalise in frost-free climates. These ferns are considered invasive in some regions such
as Australia and New Zealand. Treatment with pesticides are a challenge in water, since most
substances affect fish and the ferns easily associate with other aquatic plants such as water lilies.
When using this plant, it should be borne in mind that it might escape cultivation easily, although
they are easily controlled in smaller ponds in private gardens in Arriyadh. The attraction of Floa-
ting Ferns are the minute, exotic fronds. They grow fastest in full sun, but in Arriyadh will do
better in partial shade. The water should be high in nutrients, but the plants will thrive in almost
any environment. Propagation is extremely simple, by division.
269
Salvinia auriculata,
Salviniaceae
Floating Fern