Ray, Joost,

I've heard several people say you can cause a species Cattleya to skip a
blooming season entirely simply by having a stray light turned on in the
greenhouse overnight or if there is a streetlight shining into the
greenhouse. They are very sensitive to even small amounts of light during
the night.

-Eric in SF
www.orchidphotos.org

"Ray B" wrote in message
news:hfY9h.6079$IW2.3831@trndny03...
Joost,

If I'm not mistaken, the plants bloom in response to shortened day length,
not to light intensity directly - although I suppose there is a minimum
intensity the plants need to recognize it as "day".

Most of the time catts are forced early by covering them with black cloth
to shorten the daylength, so I'd guess that the flowering could be delayed
by keeping the day long via any sufficiently-intense light source. I
suspect that the closer the light intensity is to that of natural
sunlight, the better.