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With
more than 27 000 species,
orchids are the biggest family in
the vegetable kingdom. Much bigger
is the number of hybrids, from which
more than 50 000 have been described.
With
the exception of the glacial
and arid deserts orchids are growing
everywhere in the world, even on
Greenland some species can be found.
In the tropics orchids are extremely
numerous and colourful and are often
seen as characteristic for this
region. In Thailand alone more than
1100 different orchid species can
be found.
Looking
at their habit we can separate
between orchid plants living on
the ground (terrestrial) and those
growing on trees (epiphytic) or
rocks (lithophytic). In the tropics,
most species can be found on trees
in the upper canopy of the rain
forests, where humidity is high
year round.
In
regions, where we have
a distinct precipitation and temperature
cycle, orchids have adopted to the
dry period by storing water and
nutrients in the swollen lower part
of the stem, the pseudobulb. Succulent
leaves, formed by other species
serve the same purpose and help
reducing the loss of water by evaporation.
Epiphytic
orchids use their host
tree to come as close to the sunlight
as possible, their roots grasp and
cling to the trees without in any
way harming or taking food away
from the host, unlike a parasitic
plant. Their roots consist of a
special sponge-like layer of tissues
called velamen, that covers up the
true roots inside. This special
sheathing acts as a moisture collecting
device.
Each
orchid flower has two sets
of petals consisting of three outer
and three inner ones. While the
outer ones are similar to each other
the three inner petals will usually
consist of an identical pair and
a singular one that is unique in
size, shape and often also in colour.
This petal is called lip or labellum.
When
the pollen comes in contact
with the stigma, the bloom will
rapidly wither and the ovary will
expand into a pod. Some of them
can contain up to 4 million minuscule
seeds. As the seeds lack any nutrients,
they depend on a kind of fungi (mycorrhiza),
which is essential to help in finding
food during the first part of the
seedling's growth till it can mature
in another orchid plant. Out of
this reason cultured orchid seeds
start their life in a sterile atmosphere
on a special nutrient-rich culture
medium, before they have grown to
a size, that allows them to be fixed
to cork, coconut shells or fern
roots.
After
6 months the bottles are
destroyed and the seedlings cleaned
from the culture medium. They are
then transplanted to small pots
with coconut chips and kept under
glass to produce a moist climate.
Hybrids
are cross breeds between
natural species or between other
hybrids. The plants to be crossed
are selected for their special features
like longer lasting, larger or more
colourful flowers, longer inflorescence
and are most often easier to cultivate.
Therefore, most orchids sold in
your home country at sometimes astonishing
low prices, are hybrids. They normally
have an "X" in their name showing
from which species they have been
crossed or have pregnant names like
"Lady ..." or "Champion".
For
a collection of photos,
from orchids flowering during the
last seasons, please click here.
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