ORCHIDS
Introduction
The orchid is a very diverse family of plants, with over 20000
catalogued species, it is the largest family of flowering plants. Most
species are found in Asia. In one mountain alone, Mount Kinabalu in
Malaysia, there are over 750 species!
Growing orchids is a very rewarding exercise. A number of genera and
varieties are available today that will provide flowers pretty much all
year long. A few, such as Phalaenopsis (moth orchid), even have
attractive bold foliage and make good house plants.
Basic Requirements
All plants require the correct amount of light, air, water, food and
warmth to grow, and orchids are no exception. Most orchids in
cultivation are epiphytes (lives on trees) or lithophytes (lives on
rocks), and have a common need for good drainage. Most are grown in pine
bark which is specially processed to remove bits of wood and cambium
(the twisty pieces of bark). You can either buy bark at most garden
centres in the form of a proprietory mix, or from most orchid clubs and
orchid shows. Never plant these orchids in soil or in ordinary potting
mix.
Light
Orchids are accustomed to grow under tree canopies and will usually
require some shading from the midday sun. This can be achieved by
placing the plants on a patio where a roof or eave shades from the
midday sun; or for indoor plants, next to an East or South-West facing
window. For those with more than a few plants, it is worthwhile to
invest in a shade house.
Orchids that live higher up in the tree canopy usually require more
light than those that live lower down. If a plant looks lush, with
possibly elongated leaves or stems, it usually means it is not getting
enough light. On the other hand, if the leaves look yellowish or grows a
reddish tint, it is an indication that the plant is getting too much
light.
Orchids need the correct amount of light in order to flower, but too
much will place the plants under stress and may burn the foliage. The
right amount of light will result in good looking plants that flower
well.
Air
Plants that live up in trees have a steady supply of fresh air in the
form of breezes and the wind blowing through their leaves, stems and
roots. For plants that are grown outdoors or in a shade house, the
normal flow of air is sufficient, but for plants grown indoors, it is
important to keep windows slightly open to allow good air circulation,
without being draughty in Winter. Shade houses that normally get wrapped
up in plastic during the Winter will benefit from a small circulating
fan, and make sure the door is opened on fine days to allow for a change
of air.
Watering and Feeding
Orchids require regular watering when they are growing. For most, this
is usually during the warmer months of Spring, Summer and Autumn. Water
the pot well, making sure that all the bark is thoroughly wet and allow
the water to flow out the bottom of the pot. The movement of water
through the bark displaces the stale air inside the pot and draws fresh
air to into the pot when it drains out. Never sit the pot in a saucer of
water as the roots will rot.
Amongst orchids, Cymbidiums and Phalaenopsis hybrids are gross feeders.
Species orchids, on the other hand, tend to require much less food. Some
orchids store food in a specialised stem called a pseudobulb. It is
preferable for these orchids to be fed at every watering. A little,
often, is best.
Those orchids that have very little storage will require watering more
often. Some orchids require a dry resting period to initiate flowering.
Keeping plants dry enough in winter can not be achieved in New Zealand’s
climate unless you provide a roof over your plants.
Warmth
Orchids are found on all continents except Antarctica, and have adapted
to most habitats. Those that come from high altitude forests are very
adept at tolerating the cold, while on the other end of the scale, those
that come from balmy tropical rain forests prefer to be kept in
conditions that resemble their original home. In general, orchids are
divided into three broad hardiness categories.
Cool growing orchids can be grown in frost free areas (eg. Auckland and
north) without additional heating. Most will withstand quite low
temperatures in the Winter, as long as they are kept dry.
Correspondingly, cool growing orchids are the easiest to grow.
Intermediate growing orchids will grow in the summer just like cool
growing orchids, but require some heat over the winter. This can be
provided, for example, by bringing the plants indoors, using a heating
pad or with the aid of a greenhouse.
Warm growing orchids require warm conditions all throughout the year,
and are best grown in a heated green house or conservatory.
Pest and diseases
Healthy growing plants in ideal situations are relatively disease
resistant, so adjusting your growing area to suit your plants will pay
dividends. Spider Mite attacks in the summer if plants are too dry,
overhead sprinkling can help prevent infestations. If spider mite is a
problem leaves develop a lack lustre appearance with a silvery sheen on
the underside. Spray with miticide or if you prefer you can use the
biological approach and introduce predator mite available from Veg-Gro
outlets.
Garlic snail can attack the roots and will stunt the growth particularly
of small seedlings, they eat the growing tip out of the roots and
sometimes shoots as well. Mesurol spray or pellets are useful but do not
inhale or handle without protective clothing, Mesurol is very toxic to
humans and other animals.
Slugs and snails will chew on young shoots and flower buds. Control them
with bait.
Virus can be transferred from one plant to another by using cutting
equipment on different plants. Never use communal secateurs or the like
even to cut flower spikes. There is currently no cure and diseased
plants (and their pots) need discarding.
Use the preventive approach to control scale, as the insects are most
active in their juvenile stage and you are least likely to notice them
until a major infestation occurs. Spray with oil and insecticide
combined in October and February but do not spray when flower spikes
have buds showing as it will cause the flowers to be deformed.
Reprinted with permission from the Auckland Orchid Club.
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