requirements of plants are warmth, water, light, aeration,
anchorage and nutrients. In order to grow orchids well it is
essential to understand how their individual needs are met by
their structural adaptations to their natural habitat.
If you are just starting to grow orchids it is good idea to
visit a few orchid nurseries in the neighbor to see how they are grown. Ask
the experienced nurseryman for his suggestions as to which
plants would be suitable for cultivation indoors or outdoors.
Everything depends, of course, on where you are living. For a
start, it is important to select those orchids which are
hardy, quick to grow and easy to flower. After you have grown
some plants for a few months you will get to know their
preferences and their dislikes. Orchids are quite expressive
and if you have been treating them well they will respond by
producing handsome flower, successively larger leaves and
stronger roots which crawl all over the pot. If your handling
is wrong the plant remains stagnant. The root tops may dry up
or become shriveled-bottom leaves turn yellow and wilt, new
leaves are smaller. Of there if insufficient light the plant
turns a dark green and never flowers.
The cultivation of orchids now a
day poses few problems, particularly if one has at least a
average size greenhouse where, with up-to-date mechanical
equipment and expertise, the plants can be suitably
Orchids are classified into
three categories on the basis of their temperature
These orchids grow best at
night temperatures of 10-13 degrees centigrade and day
temperature of 16-21degrees Centigrade. They come from the
mantane regions of the tropics, e.g the large flowering
Cymbidium, Odontoglossum, Miltonia etc. These plants have
feeble growth in warm climates and never flower. Some
attempts have been made to hybridize them with warm
growing orchids (e.g.interspecific breeding in Cymbidium).
2 The Intermediate Group
This group embraces the
broadest collection of cultivated orchids and these plants
prefer night temperature of 10-16 degrees Centigrade and
day temperatures of 21-29degrees Centigrade. Cattleya,
Oncidium, Dendrobium nobile, some Paphiopedilum,Epidendrum
and a whole range of interesting botanicals belong to this
group. Several orchids which usually grow in a warmer
climate, e.g. Phalaenopsis, Ascocentrum and Vanda, will
also thrive in the warmer parts of the intermediate orchid
3. The warm-growing
night temperatures which are consistently above 16 degrees
centigrade for proper growth and they are all natives of
the tropical low-lands. During the day, especially in
summer, it can be allowed to rise 30-32 degrees centigrade
without the plants coming to harm. All members of the
monopodial Vanda-Aerides tribe, including Phalaenopsis,
belong to this group.
This is the
prime importance for the plants and consequently their
capacity to produce flowers. In this context orchids may
be divided into three major groups: those that live in
full shade, in full sun and in an intermediate situation
the majority of orchids are epiphytic, it is the third
condition which is most common. They receive only dappled
sunlight through the forest canopy. Such orchids require
25-50% shade in summer if they are cultivated in temperate
regions and throughout the year if they are grown in the
tropics. The Dendrobium, Cattleya, Phalaenopsis and
strap-leaf Vanda belong to this group. Some members of the
Arachnis –Vanda (or Aerides) tribe are grown in full blast
of the sun throughout the year. The only parts of the
plant which may be shaded are the feeding roots which are
hidden in the undergrowth. These orchids and their hybrids
like full sun throughout the year and will only flower if
they receive strong sunlight.
The terrestrial orchids have
a much lower light tolerance for thy grow either in the
deep shade of the forest, in bogs or in open bush-land
where they are protected from the full sun by other plants
growing in the bush. Under cultivation, these require
60-75% shade. Examples are Paphiopedillum, Cyperipedium.
Shade in the greenhouses may be provided with nets of
varying sizes of mesh and preferably of a dark color, with
matting, or with white paint on the outside of the
panes-all easily removable when no longer necessary.
The type of
lights is also important for proper growth of the orchid.
Light in the ultra-violet, and green ranges represses
plant growth and green PVC (poly venyl chloride) sheets
are totally unsuited for roofing of orchid houses. When
too much green algae collect on top of the plastic roofing
it similarly represses plant growth. The algae must be
scrubbed off or the roofing replaced.
growth, orchid can be grown in continuous light day and
night to achieve maximum growth. However, day length, or
more correctly night length, affects flowering. Increased
light, higher humidity and lower day temperature would
always lead to better growth and flowering.
A high level of
surrounding humidity is essential for plants that
originally come from tropical zones; in no instance should
this below 50%. A rise in temperature means a drop in
humidity, so during the warm months of the year various
methods have to be used to control level. Humidity can be
increased by damping down the greenhouse paths and the
areas beneath the shelves, or by using humidity trays
indoors. Here the floor should be of clay, sand or gravel,
which gives off moisture.
The most widely
collected orchids are for the most part epiphytes and can
be cultivated in supports with the roots left to grow in
the air. Epiphytic orchids cannot be potted in soil
because their roots require good aeration. If they are
waterlogged they soon begin to rot. As the plants grow and
are repotted into successively larger pots, bigger pieces
of crocks, charcoal, fir bark or tree fern have to be
added to ensure that water is drained off effectively
after it has wet the roots. After two or three years, the
root ball becomes too extensive and the potting medium
would have deteriorated and collapsed, causing a
constriction of the air spaces which then become
waterlogged. To avoid this, most growers repot at least
once in two years. An alternative approach is to remove
the forward bulbs from the back-shoots to produce keikis
which can be removed and repotted wherever they produce
Air that is
constantly moving is a good guarantee of health in
orchids. Commercial growers pay lot of attention to wind
movement when selecting a site for an orchid nursery.
Strong wind movement is favorable and good site should
have sloping terrain and should be obstructed by tall
structures. Orchid leaves are heated by radiant energy and
can only lose this heat by conduction into the atmosphere.
It is therefore important to have good air movement and
high humidity around the plant since water conducts heat
more efficiently than dry air. If the plants are watered
in the evening, a strong currents will also lower night
temperature and induce flowering.
A greenhouse for
orchids, whether hot, temperate or cool, should be a
pleasant environment. A well-ventilated greenhouse
receives good circulation of fresh air. Ventilation lowers
the temperature, and dries out and eliminates any standing
water that is especially likely to harm the plants when
the temperature goes down. In well ventilate surroundings
plants are not seriously harmed by temperature several
degrees lower than the minimum recommended. An adequate
circulation of air, together with suitable heating of
greenhouse will prevent many fungal and bacterial attacks.
The answer to
the question “How should I water my orchids?” is no easy
because it depends on many factors. Are the plants in a
pot or on a raft? What soil is being is used? Adult or
young plants? Where have been grown? First of all, one has
to know the cultural requirement of the plants,
particularly in relation to their rest period. In the
cool, temperate regions, plant growth slows down in autumn
and may come to a halt in winter. Watering should be
reduced during this period.
As a rule,
plants grown in a raft, whatever the constituent material,
should be sprayed very frequently, even several times a
day in the growing season, and watered plentifully at
least every other day. For plants kept in pots, it has to
be remembered that growing longer than bark, charcoal and
perlite. These materials may be used either pure or mixed
in different proportion, according to the needs of the
lighter, unbreakable and easy to disinfect, retain
moisture better and longer than clay pots or baskets.
Young plants, with a less-developed root system and more
delicate growth, need watering more often than adults of
the same species.
Given all these
consideration, it is fair to say that adult plants, grown
in plastic pots, with bark, should be watered in average
once every 5-6 days, and although this may vary by a few
days either way depending in the alternative factors
It is best to
water orchids in the morning, preferably in a fine day, so
that any standing water, harmful to the health of the
plants, can disappear by evening.
There is no doubt
that orchids benefit from the application of fertilizer. A
fertilizer equally balanced in nitrogen, phosphorus and
potassium (18-18-18), dissolved in the ratio of 1 gram to
1 liter and applied once a week for approximately ten
months (from late spring to early winter), and a food
containing more nitrogen (30-10-10) during the remaining
part of the year will provide a sufficient supply of
nutrients to give luxuriant, free-flowering plants.
Nitrogen is necessary for the formation of proteins and a
good supply of nitrogen is the key to rapid vegetative
growth. However, continued application of high nitrogen
fertilizers produces soft growth and may delay flowering.
It is advisable to
water the plants abundantly prior to feeding in order to
wash any residues of mineral salts and to wet the roots in
preparation for a new feeding. An accumulation of salts
cause serious scorching of
the roots, especially if the compost is not sufficiently
Orchids as a
rule are repotted every three years. The best time to do
this is when the plants resume their growth and the new
roots begin to sprout.
roots are fleshy and sometimes fragile, they need to be
fairly dry when handled so that they quickly, start to
grow again and branch out. Compost for repotting should
therefore be moist but not waterlogged. If bark is used,
choose pieces in the dimensions as per the plants size.
After a plant has
been removed from the old compost, rotten roots,
pseudo-bulbs and dead stems should be eliminated; the
plant then be replaced in a new pot of suitable dimension,
and positioned either center or off-center according to
its structure, so that as much space as possible is left
for its growth. The compost should be placed between the
roots and firmly pressed down so as to give the plant
stability. If necessary the plant can be tied to a stake.
Unlike most plants, orchids need not be watered after
repotting for atleast two weeks, until the roots start
growing again. Frequent spraying and a high level of
surrounding humidity will help the plants weather this
Carbon copies of
the orchid can be produced through the vegetative
propagation which can be achieved by four methods:
the plants, otherwise know as cutting.
development on old back bulbs.
plantlet formation on flower stems.
This method is
suitable for both monopodial and sympodial orchids. In
case of sympodial orchids, the following conditions should
be made before dividing the plants:
It should be
healthy. If the plant is weak, it is better to remove a
It should have
four matured stems, preferably more.
pseudobulb should be developing from the base of the old
one and just beginning to send out its own roots.
A clean cut is
made in the rhizome, leaving at least two mature
pseudobulbs attached to the young one to provide it with
nourishment. After sealing off the cut ends with fungicide
or tar, divided plant can be left in the pot or the
younger segment can be removed and repotted. The back
portion will produce at least one new pseudobuld if it is
If the original plant is
large and extensively branched, several cuts can be made,
each segment to be left two or three strong pseudobulbs
will develop, one or two behind each cut on t horizon. If
the plant is left in the pot, it will produce a
spectacular flowering when all the new pseudobulbs send of
When doing this, it is
customary to trim off all the old roots, but many growers
will leave the old roots behind if they are healthy and
still capable of absorbing water and nutrients. Clear off
all the old potting medium and soak the roots in fungicide
In case of
monopodial orchids the optimum time for cutting is:
When the top
cut portion will have at least three strong roots, and
segment is left with at least six leaves and four
unflowered leaf axils.
a clean cut with pruning shears, not with a knife. Seal
off the cut ends with coal tar or a fungicide and allow
the tip to dry before replanting the top portion. After a
few weeks the bottom segment will produce several new
shoots and when these have developed two or three strong
aerial roots, they may be removed and replanted.
If the aim is to
propagate the plant, it should be given 50 per cent or
even heavier shade, liberal watering and heavy nitrogen
feeding. This will stimulate rapid soft vegetative growth
and prevent flowering. Take care to spray fungicide at
close intervals because under such growing conditions the
plant is prone to bacterial and fungal rot. When making a
top-cutting, more of the stem is left behind in order to
obtain additional offshoots. If the offshoot is very
strong, and there are no more axillary buds left on the
main stem, it need not be removed completely; instead a
short stump of the offshoot bearing two or four leaves can
be left behind on the old stump, and this in turn will
yield another generation of offshoots.
A higher yield can
be obtained by making multiple cuts on the stem but this
can only be done if the plant has been grown so that its
roots are firmly attached to a broad stump of wood. Each
division should have six leaves and they are al left
attached to the original support. Shading is increased,
and liberal watering and heavy nitrogen fertilizer is
given. After a few weeks, three or four offshoots will
develop from each segment. When these are strong enough,
they may be removed and repotted.
Treatment of black bulbs
Instead of removing the new
lead as described above, one or two old pseudoublbs at the
end of the rhizome may be removed. This may actually
strengthen the plant left in the pot. The pseudobulb is
hung up under shade and watered occasionally until a new
shoot develops, when it can be replanted in the usual way.
If the lowest bud is healthy it will be the one to develop
into a now shoot; otherwise any bud along the length of
the pseudobuld may develop into a new plant. Various
methods are employed to increase the humidity around the
back bulbs to encourage the development of offshoots. Some
of these are layering on peat and sand, or dropping back
bulbs into a polythene bag which contains a small amount
of moist sphagnum moss.
Plantlets from flower stem
plantlets on the flower stem is commonly exhibited by
Phalaenopsis and its intergeneric hybrid, and the old
inflorescences of Oncidium, although, vary rarely, the
flower stems of Dendrobrum may become vegetative and turn
into a plantlet. Old of such species should always be left
on the plant after flowering for they are frequently the
source of bonus plants. Plantlets so develops are known as
Kiekie. Some orchidists developed a paste which caused
Keikis to develop on the flower spike. An aqueous cream
with 0.05 to 0.5% benzyl adenine when applied to flower
spikes caused the axillary buds to soil and in most
instances to develop into single plants or clumps of
plants. To obtain a 0.05% concentration, mix 0.5mg of
banzyladenine with 1g of cream or lanolin. Select only old
flower spikes which have finished flowering a few weeks
earlier. After removing the bracts from the two internodes
beneath the first flower, apply the paste lightly to the
bud. These axillary buds will swell after four days and
the first leaves will break through after a fortnight.
After two or three months some plantlet will develops
roots; a few may take longer. Leaves of these plantlets
are vary succulent until the have developed strong roots.
It is a temptation to apply deepest on all the nodes on
the flower spike but this will probably weaken the parent
plant and the benzyl adenine may inhibit the growing point
on the plant. It is safer to produce only one or two
plantlets on a single inflorescence. On the other hand, if
the parent plant is dying from crown rot or weevil attack,
then one may feel free to treat all the axillary buds.
Amongst the many
floral treaties of Sikkim Himalaya one of the earliest ones may be
found over the genus Rhododendron (Gk. rhodo = red, dendrons = tree
known for their brilliance in colors, unusual shapes
attractive growth habits, variety in fragrance and
exquisite beauty can attract any nature lovers.
with its total geographical area of 7,096 sq km is
bestowed with a huge diversity of flora and fauna.