The Oncidium - Flowering
Depending on the variety, the flowering season can be at any time
of year, but is generally heaviest in the Fall and Spring.
Many hybrids can bloom 2-3 times per year. In order to initiate
the flower spikes, it is important to grow the plant in an area
where the night temperatures fall below 65 degrees.
Usually plants growing by a window are a couple of degrees cooler
than the rest of the house.
The Oncidium - Light requirements
Can be from just bright to almost full direct sun depending on
the plant. Most will thrive with one to several hours of sun a day.
Generally, thicker-leaved plants can stand more light, such as
"mule-ear" and "equitant" oncidiums.
In the home, east, south or west windows are ideal. Many types
will grow under artificial light: four fluorescent tubes 6 to 12
inches over the plants are necessary for proper growth.
Metal-halide and sodium vapor bulbs also provide sufficient light
without needing to be so close to the plant.
In a greenhouse, 20% to 60% shade is required or about 2,000 to
6,000 footcandles, depending on the plants grown.
The Oncidium - Temperatures
For this group are generally called intermediate to warm: 55 to
60F at night, and 80 to 85F during the day.
Temperatures to 95 to 100F are tolerated if humidity and air movement
are increased as the temperature increases
The Oncidium - Required Watering
Requirements vary with the type of plant.
Generally, plants with large fleshy roots and/or leaves need less
frequent watering than thin-leaved and/or thin-rooted plants.
Watering should be thorough, and plants should dry at least halfway
through the pot before watering again. this may be every 2 to 10
days depending on weather, pot size and material, type of orchid
and type of medium.
Plants not actively growing should be watered less; many species
have winter rest periods.
You should consult your grower for detailed instructions specific
to your variety of plant.
The Oncidium - Necessary Humidity levels
Should be between 30% and 60%.
Most of these orchids require less humidity than some other orchids.
In the home, placing the plants on trays above moist pebbles is
ideal.
Misting the plants in the morning may help increase the humidity
but is usually not recommended for fleshy leaved types.
Most greenhouses have adequate humidity
The Oncidium - Chilling Injury -
Cut Flowers
These plants have flowers that are failry
sensitive to "chilling" injury. Holding the flowers for any length
of time at temperatures below 10° C (50° F) will induce purpling,
browning around the edge, and then necrosis.
Oncidium Blooms should therefore never be pre-cooled with other
flowers, nor held in low temperature cool-rooms below 50 degrees
F..
The Oncidium - Fertilizer Requirements
Should be applied regularly while the plants are actively growing.
Applications of 30-10-10 formulations twice a month are ideal for
plants in a bark-based medium.
A 20-20-20 formulation should be used on other media or on slabs.
If skies are cloudy, applications once a month are sufficient.
Some growers use a high phosphorous, 10-30-20 formulation bloom
booster as plants approach blooming.
The Oncidium - Potting & Re-potting
When new growth begins from the base of the plant, which is usually
in the spring.
A fine grade potting medium is usually used with fine rooted plants
and coarser mixes with larg-rooted plants; the standard size is
medium grade.
Usually the lowest one quarter to one third of the pot is filled
with drainage material, either crock shards, rocks or styrofoam
'peanuts'.
The plant is positioned so that the newest growth(s) are farthest
form the edge of the pot, allowing the maximum number of new growths
before crowding the pot.
Spread the roots over a cone of the potting medium and fill in
around the roots. Firm the medium well around the roots by applying
pressure.
Keep humidity high and the potting medium dry until new roots form.
A vitamin B1 compound may help establish newly potted plants. "Equitant"
and "mule-ear" oncidiums, as well as other fleshy-leaved
or large rooted plants, can be grown on slabs of cork bark or treefern
or in pots of a coarse, well-drained medium such as charcoal.
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