INTRODUCTION: The orchid
family is a very large group of monocots. It is one of the most recently evolved
plant families. Divisions among species and general are not distinct and many
intergeneric hybrids exist. Orchids are found in nearly every climatic zone from
arctic to tropic and on all continents except Antarctica. Many are native to higher
elevations in the tropics and grow best at cool temperatures year round. There are
both terrestrial and epiphytic types. Seeds of orchids are extremely small, about
the size of particle of dust. The vanilla orchid is the original source of natural
Epiphytic orchids are divided into two groups,
sympodial and monopodial, based on their stem structure. Monopodial orchids grow
upright and develop side shoots, which also grow upright. They bear their leaves in
two ranks, perpendicular to the stem and do not produce pseudobulbs. Sympodial
orchids often have pseudobulbs, a thickened stem from which the leaves arise. Their
growth is horizontal, the pseudobulbs being attached to a common basal rhizome.
Growth of the pseudobulbs and extension of the rhizomes develops out of the base of the
old pseudobulbs. These pseudobulbs store food and water and enable the orchid plant
to withstand periods of drought.
Cattleya is the
genus most people think of when they hear the word orchid. Although they come in a
wide range of colors and color patterns, the color orchid is named for one of the flower
colors found in cattleyas. Most cattleyas make the large, showy flowers common
in corsages. They are tropical epiphytes with sympodial growth and pronounced
pseudobulbs. They are native to higher elevations in Central America and northern
South America. They grow best in warm, but not hot, conditions and grow and flower
best at brighter light, brighter than that preferred by most orchids.
Dendrobium is a
sympodial epiphyte native from India to Japan and Australia. There are several
subtypes with distinctly different cultural requirements. These include the
pseudobulb dendrobiums, evergreen cane dendrobiums, deciduous cane dendrobiums, evergreen
phalaenopsis type dendrobiums, and black hairy-stemmed dendrobiums. Dendrobiums vary
in the cultural requirements, some needing uniform moisture, others a period of drought;
some needing seasonal changes in temperature, others uniform temperature; some needing
diurnal changes in temperature, others not, etc. Many dendrobiums produce smaller
flowers but in large sprays. Many need a dry period prior to bud development.
Laelia is a genus
of orchids closely related to the cattleyas. They are epiphytic, evergreen orchids with
pseudobulbs. The flowers of laelias have a distinct resemblance to cattleya flowers.
The genus Miltonia
is native to Central and South America. These are the pansy orchids, so named
because their flowers resemble the flat-faced pansy flowers. Culture is similar to
cattleyas. Some miltonias have a distinct preference for cool temperature and most
thrive in indirect sunlight.
Oncidium is a
sympodial, epiphytic orchids native from Mexico to Brazil. Like dendrobiums, many of
the oncidiums produce large sprays of smaller flowers. Oncidiums have a range in
temperature requirements depending on the species, but most do best in when given a lot of
sunlight and a rest period of several weeks following the development of their new growth.
the lady slipper orchid. It is a terrestrial orchid. This genus is adapted to
a wide range in temperature conditions, some being decidedly tropical and others almost
temperate. They thrive in bright, though indirect light. They lack pseudobulbs
and can not store water.
is the genus of the moth orchids. They produce large, moth-like flowers in a plane
along the two sides of a long, arching stem. They are monopodial, epiphytic orchids
native to south Asia and Australia to west Africa. They thrive in a diurnal
temperature fluctuation of 65oF night to 75-80oF day. They grow and flower at lower
light than most orchids, often thriving in indirect light. Moth orchids thrive at
The genus Vanda is
native to southeast Asia. It is a group of monopodial orchids with either strap
leaves or pencil leaves. Vandas can not tolerate temperatures below 50oF for any
period of time and thrive in a very humid setting with good air movement. They need
plenty of water but must have excellent drainage. Most thrive in settings with relatively
Vanilla is a
monopodial orchid. It produces a heavy, succulent vine and is relatively east to
grow. Unfortunately it is one of the more difficult orchids to bring into flower.
General Care of Orchids:
||Most tropical orchids grow best at a
uniformly warm, but not hot, temperature. Some orchids thrive at cooler
||Epiphytic orchids require good drainage
and aeration of their roots. Coarse media such as tree bark, osmunda fiber or moss
mounted on tree bark are common. If potted in common media, such as the peatlite
mix, orchids usually fail to thrive and eventually die. Terrestrial orchids thrive
in a rich, organic medium that drains well.
||Most orchids grow best in a humid
environment with good aeration. They should be watered to keep the medium
moist. For epiphytic orchids potted in a well drained, airy medium this may be twice
a day. Orchids can not tolerate a wet medium.
||Orchids occur in many different
environments and this affects their light requirements. Some grow near the tops of
trees in rainforests. They need brighter light than others which may be found
growing in denser forests and at lower levels in the tree canopy. Terrestrial
orchids in cultivation are usually found on the forest floor and grow well in moderate
light. Most orchids need protection from hot, midday sun in summer, but could be
grown in direct light in other seasons.
||Orchids need a steady supply of nutrients
but can not tolerate salts. Dilute solutions of inorganic fertilizers are common or
organic sources of nutrients are used.
|pests and problems:
||Protecting the roots from rot is
essential. This is done by using the proper medium for the type of orchid that is to
be grown. Pests are relatively few on orchids but diseases of the leaves and stems
may be a serious problem, disfiguring or killing them.
||Remove old parts of the plant after
nutrients have been translocated to the new growth.
||Seed of orchids is extremely small
and is usually planted on an aseptic medium such as agar. Seed is the only way to
propagate some orchids, but others may be propagated by division, separation and
stem cuttings. Asexual micropropagation, a process commonly called mericloning, is
done by excising the meristem of a plant, culturing it aseptically to form a mass of cells
and then triggering the development of many plantlets from this mass of cells.