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Odontoglossum Alliance

Cool-Growing Genera

These New World Tropics, high-altitude orchids are popular
where cool temperatures prevail. The Colombian miltonias (truly
Miltoniopsis) and showy odontoglossums have striking sprays of
flowers. Culture is similar for hybrids in this group, some
being Odontonia, Odontioda and Vuylstekeara.

LIGHT levels should be bright. An east window or a shaded south
window in the home is ideal; western exposures are usually too
warm in most climates. In a greenhouse, levels from 2,000 to
5,000 foot-candles are acceptable; some Miltoniopsis growers
demand the pink flushing in the plants' leaves which results
from the high light levels. If summer day temperatures are
high, light levels can be reduced to cool the growing area.

TEMPERATURE is critical for these plants; day temperatures
below 75 to 80 degrees F are preferred year-round. Night
temperatures of 55 to 58 degrees F are best. Short periods of
warmer day temperatures may be tolerated, especially if
humidity and air movement are at optimal revels and nights are
cool. Miltoniopsis plants prefer night temperatures at the
upper end of the range while many odontoglossums thrive at 50
to 55 degrees F at night.

WATER should be plentiful, coupled with perfect drainage. The
potting medium should just start to dry before watering again.
"Accordion-pleating" on miltonia leaves is a symptom of
insufficient water or humidity, and may appear on plants of
other genera if severe. This may mean watering every two to
seven days, depending on weather, pot size and material, and
type of potting medium.

HUMIDITY ideally 40% to 80%, is important for all these
orchids, coupled with moving air. In the home, set the plants
on trays above moist pebbles, with the pot resting above the
water. Misting is beneficial, but in the mornings only.
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.

FERTILIZER should be applied regularly 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 or on slabs.
If weather is dull applications once a month are sufficient.
Some growers use a high-phosphorus 10-30-20 formulation bloom
booster as plants approach flowering.

REPOT as new growth emerges from the base of the plant which is
usually in the spring or fall. These orchids like to be very
pot-bound, so when repotting leave only enough room for one to
two years of new growth. A fine-grade potting medium with
excellent drainage is required; since the medium is kept moist,
annual or bi-annual repotting is normal. Usually the lowest
one-quarter to one-third of the pot is filled with drainage
material, either crock shards, rocks, or Styrofoam "peanuts".
Spread the roots over a cone of potting medium and fill in
around the roots with potting medium. Firm the potting medium
well around the roots by applying pressure. Keep humidity high
and the pot dry until new roots form. A vitamin B1 compound may
help establish newly potted plants.

Prepared by: Education Committee, American Orchid Society
6000 S. Olive Ave., West Palm Beach, FL 33405 (407) 585-8666.

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