These high-altitude orchids
from the New World Tropics flourish where cool
temperatures prevail year round. Odontoglossums
are known for their striking sprays of flowers.
Culture is similar for hybrids in this group,
some being Odontonia, Odontioda and Vuylstekeara.
L I G H T
should be bright. In a greenhouse, levels from
2,000 to 5,000 foot-candles are acceptable as
long as heat levels can be kept down. If summer
day temperatures are high, light levels can be
reduced to cool the growing area. While these are
not generally considered to be good houseplants,
they may succeed at an east window or a shaded
south window; western exposures are usually too
warm in most climates.
T E M P E R AT U R E S
must be exacting for these plants. Day
temperatures below 75 to 80 F are almost
essential year round. Night temperatures of 55 to
58 F are best. Short periods of warmer day
temperatures may be tolerated, especially if
humidity and air movement are at optimal levels,
nights are cool and the plants have healthy root
systems.
W A T E R
should be plentiful, coupled with perfect
drainage. The potting medium should just begin to
dry before watering. This may mean watering every
two to seven days, depending on weather, pot size
and material, and type of poring medium.
Accordion-pleating on leaves is a symptom of
insufficient water or humidity. As with other
orchids from high-rainfall areas, odontoglossums
are particularly sensitive to poor-quality water,
which will give poor roots and leaf-tip burn.
H U M I D I T Y,
coupled with moving air, should be ideally 40 to
80 percent. Evaporative cooling in a greenhouse
increases humidity while cooling the air and is
highly recommended for these orchids in most
climates. Fogging the air or dampening the floor
with water also helps cool and humidify. In the
home, set the plants on trays above moist
pebbles, with the pots resting above the watch
F E R T I L I Z E
regularly with a dilute solution while plants are
actively growing. Applications of 30-10-10
formulations twice a month are ideal for plants
in a bark-based potting medium. A 20-20-20
formulation should be used on other media. If
weather is overcast, applications once a month
are sufficient. Some growers use a
high-phosphorus 10-30-20 blossom-booster
formulation as plants approach flowering to
increase flower count and substance.
P O T T I N G should
be done as new growth becomes about half mature,
which is usually in the spring or autumn. These
plants need to be underpotted, so when repotting
leave only enough room for one to two years of
new growth. Underpotting also enables the grower
to provide the more frequent watering these
plants need as the smaller pots dry more quickly
and evenly when filled with roots. A fine-grade
potting medium with excellent drainage is
required; because the medium is kept moist,
annual or biannual repotting is normal. Spread
the roots over a cone of potting medium and fill
in around the roots with more medium. Firm the
potting mix around the roots. Keep humidity high
and the pot dry until new roots form.
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Prepared by the AOS Education Committee