The Orchid Doctor Articles under the Heading Photoperiodism

Photoperiodism Comments
PHOTOPERIODICITY: Affected by Use of Electric Lamps A green lamp of low wattage can be used for working at night in a greenhouse; moderate light for about two hours before 10 o'clock or 11 o'clock has little effect, but more effect if burned in the middle of the night. A69-242; refer also to A61-106 0
PHOTOPERIODICITY: In Cattleyas Plants set their buds in a certain daylength; artificial light in a living room where plant is growing lengthens the day and prevents bud set. A70-344 0
PHOTOPERIODISM: Effects of Day Length At three degrees north of the equator the difference between the shortest and longest days of the year is 20 minutes yet orchids bloom seasonally. A61-105 0
PHOTOPERIODISM: Hours of Complete Darkness Needed by Cattleyas There is no generally recognized rule-of-thumb; in general 12 to 15 hours tend to favor flowering; eight to nine hours tend to stimulate vegetative growth; some summer-flowering cattleyas fall between the two. A64-1074 0

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