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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 orchid 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 orchid 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 orchid 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 orchid 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 orchid 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 orchid 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 orchid 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 orchid species
or between other orchid 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 well-sounding names like "Lady ..." or "Champion".
For
a collection of photos, from orchids flowering
during the last seasons, please
click here.
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