Orchids are considered
as the most beautiful flowering plants for the exquisite beauty of the flowers, variety of
fragrance, brilliance in colour, unusual shapes, variation in form and attractive growth
habits. There are about 24,000 species and 32,000 hybrids of orchid.
Development of new
hybrids and commercial production of cut flowers in orchids are expanding rapidly in the
U.S.A. Europe, Thailand, Malaysia and Singapore. There is immense scope for improving
orchids in India, because large number of species are native to this country and many of
them have already proved to be important parent plants and contributed in the production
of several outstanding hybrids in the world. Due to the diversity of environmental
condition in India, it is possible to grow all types of orchids in suitable places without
the control of environment.
Forest is the natural
habitat of orchids. More or less similar environment can be created by growing the plants
in greenhouse and protecting them from direct scorching sun, dry wind and by maintaining
Warm Climate Orchids:
Orchids which suit
warm climate condition and can be successfully grown in ordinary greenhouse include the
numerous hybrids of Cattleya, Dendrobium, Onicidium, Phalaenopsis, Rhynchostylis and
Vanda, Orchid species producing beautiful flowers e.g. Aerides longicornu, A. multiflorum,
Arachnis crispum, A. maculosum, A. odoratum, Anoectochilus roxburghii, Arachnanthe
catchcartii, Arundinia bambusaefolia, Calanthe densiflora, C.masuca, Coelogyne flaccida,
C.ochracea, Dendrobium aggregatum, D.densiflorium, D.devonianum, Phaius macutatus,
P.wllichii, Phalaenonsis manii, P. parishii, Pleione maculata, Renanthers imschootiana,
Rhynchostylis retusa ,Saccolobium ampullaceum S. dasypagon, S.trichromum, Thunia
alba,Vanda coerulea,V.coerulescens, V.cristata, V.teres and many others grow and flower
well in the above enviornment.
Orchid House And Its Management: -
A free standing
flat-roof orchid house shaded by spit bamboo or wooden batten is recommended for housing
of orchids suitable for warm climate. The temperature range suitable for most of those
orchids is 65 to 850F. For satisfactory growth of orchids, atmospheric humidity
should not be less than 30 per cent at night and 70 to 80 per cent during the daytime.
Monopodial orchids like Vanda, Phalaenopsis require high humidity, whereas sympodial type
e.g. Cattleya, Laelia or those with leathery leaves need less humidity. The atmospheric
humidity will increase if small tanks or lily pools are located inside the orchid house
and the floor space is covered with sand, soil, cinder, etc. instead of concrete. Free
circulation of air is needed for the orchids to grow and flower and light intensity
ranging between 1500 to 2000 feet candle in midday is good enough for most of the orchids.
Seed Sowing and Care of Seedlings: -
Seedpod of orchid grow
after fertilization, and ripens in six months to one year. After ripening the seeds are
collected and stored in a cool and dry place or in a desiccator. Millions of powdery seeds
are released from each pod and they contain little or no food to nourish the embryo. Under
natural condition, the seeds germinate when they find a right pocket of decaying vegetable
matter on the trees.
Seeds of orchids are
germinated and seedlings grown in culture media containing agar, inorganic nutrients and
sugar. Disinfected seeds are sown in sterilized flasks containing agar-nutrient media and
the seedlings grow for 8 to 12 months before they are transferred.
The seedlings are
removed from the flask and planted in the community pots, 7 to10 cm in diameter which hold
about 20 to 25 small plants. The compost used for seedlings in the community pot is a
mixture of equal parts of the finely chopped tree fern and dust-free crushed bark or moss.
A shady but well aerated location in the greenhouse will promote the growth of seedlings.
In the community pot, the seedlings are watered daily and during the summer months they
may be sprayed with water two to three times a day.
With the increase in
size and vigour, each plant is transferred in a small pot, using the same compost
recommended for larger plants, but at this stage they benefit by feeding with the weaker
concentration of fertilizer solution.
Vegetative Propagation: -
by seeds, commercial method of vegetative propagation of hybrids of Cymbidium,
Phalaenopsis and Cattleya is done by meristern culture and large number of plantlets
develop from a small piece of growing apex. Amateurs, however, propagate their plants by
offsets, air layering, cuttings and division. Offsets develop from Dendrobium and some
Epdiendrum, which can be detached and planted in small pots.
Air layering is
practised on the monopodial types like Vanda. A slant cut is given halfway in the stem and
wrapped with sphagnum moss. When roots are noticed in the moss, the upper portion of the
plant with roots is detached and potted.
Renanthera and to a lesser degree in Vanda propagation is done by cutting. As these
large-sized plants produce adventitious roots, the stem is cut in section 3 to 4 nodes,
placed in a cool and dry place for healing of wound and allowed to root in moist sand or
damp sphagnum moss. Plants of many genera such as Cattleya, dendrobium, etc., produce new
growth from a lead and they can be propagated by division at the time of repotting.
Potting and Compost:
A vigorous and healthy
root system often indicates good vegetative growth of the plants, which largely depends on
the pot compost. Ideal rooting media will provide high degree of porosity and ensure
adequate oxygen for root respiration. Water should drain out freely through the media and
it should be resistant to rapid decomposition and decay.
Depending on the
growth habit, i.e. terrestrial or epiphytic, orchids are potted in a wide variety of media
and compost. Epiphytes like Cattleya, Epidendrum, Phalaenopsis Vanda, Dendrobium,
Rhynchostylis, etc., are planted on a very light rooting media, consisting of various
kinds of tree fern fibre or on larger pieces of hard charcoal. Terrestrial orchids like
Phaius, Calanthe, Thunia, etc., thrive best in the mixture of leafmould, loamy soil,
sliversand, dried cowdung manure, charcoal and chopped tree fern fibre. Epiphytic orchids
are best grown in speciality designed orchid pots with holes at the bottom and slits or
perforations on the sides. Monopodial epiphytes like Aerides, Phalaenopsis, Vanda, etc.,
are particularly suited to basket culture because of the large aerial roots produced from
these plants and straight growing habit. Many orchids are conveniently grown on the
branches of the trees, charred wooden slabs or tree fern blocks.
Orchids grow better if
undisturbed, Phalenopsis, Vanda, Laelia and some species of Dendrobium should not be
repotted unless it is absolutely necessary. Cattleya and many Dendrobium species and
hybrid need repotting when roots become pot-bound.
Watering and Spraying:
As orchids are grown
in a light and porous compost, watering is very important. Atmospheric humidity influences
evaporation of moisture from the compost and orchids, in general, prefer high relative
humidity. In a dry and will-ventilated atmosphere, damping down of the floor of the
greenhouse, frequent overhead sprinkling of water will increase the humidity. But in high
humid atmosphere watering should be less frequent. Alkaline water is injurious to orchids
and slight acidic water or at pH up to 7 should be used.
Newly potted plants
should not be watered very frequently but the compost is kept moist by fine spraying. As
new root emerges and growth starts, the plants need more frequent watering and it should
be decreased again after flowering. Fine spraying of water is also very beneficial to
plants during the period of growth or on warm dry days.
It has been observed
that growth and flowering or orchids are improved markedly by the application of
fertilizers in liquid form and a number prepared fertilizers are available in the
orchid-growing countries. A balanced feed on nitrogen, phosphate and potash in the ratio
of 10:12:10 and very small amount of magnesium, calcium, manganese, iron, boron and zinc
has been found very effective on a large number of species and hybrids. For mature and
flowering plants. Two table spoonful of the above fertilizers mixed in 10 litres of water
is sprayed once a week, while a more dilute solution is used on seedlings. Leaves and
rooting media should be thoroughly sprayed with the fertilizer solution.
Diseases and Pests:
Orchids are less
subjected to the attack of pests and disease. Scale insects, mealy bugs, green fly,
thrips, red spider and snails may cause considerable damage, fly, thrips, red spider and
snails may cause considerable damage, if they are not controlled in time. Application of
Rogor or Malathion is very effective to keep the orchids free from pests.
Die-back is a serious
disease in orchids which starts in rhizome and if left unattended, it spreads to other
plants in the orchid house. Orthocide 50 and Cossan are recommended for controlling fungus
diseases on orchids. Virus infection is also common in several species and varieties of
orchids. Sometimes black spots appear on leaves and flowers turn yellow and drop off. This
is not caused by fungus but due to faulty culture like over-watering insufficient
ventilation, too much of light or very dry atmosphere.
Cleanliness of the
greenhouse and regular attention to the plants are very important to keep the plants free
from diseases and pests.