I live in northwest Illinois and grow several clones of paph. delenatii that
bloom regularly in the spring...usually March. My potting medium consists
of medium fir bark, large perlite, medium charcoal and oyster shell
chips...all these are in equal parts. I also let the plants dry thoroughly
between waterings and keep them somewhat drier in the winter...and also
cooler. I grow in a greenhouse with winter temps in low 50's and low 70's
during the day. During the summer I grow as low as possible during the
night and try to keep the temps below 90 during the day. I do not have an
evaporative cooler but do have a misting system that goes on when the
humidity drops below 50%. I hope this helps.
Marcia Whitmore
http://www.netexpress.net/~whitbrits/myorchids.htm