Could you look into adding some polycarbonate sheets onto your back porch?
They can be made removeable and cut to any size to fit the openings you
have. That way you can have an unheated sun room in the winter, move your
plants out in Spring without worry and then remove them for the summer. Here
in SC, plants like amaryllis, cymbidiums, azaleas, and primulas bloom all
winter on the back porch visible through the sliding glass doors. If the
temps go below 20 outdoors (a few times a winter) then we either move the
plants in or crack the door to circulate some heat to the porch. Twinwall
holds in the heat very well and has been a great investment.
Gary

"C. Berlin" wrote in message
news:KANUj.24551$qW.13459@trnddc06...
I have a small collection with a lot of phals, and a few dendrobiums,
paphs, cymbidiums, masdevalias, oncidiums, lc, and a brassia,
odontoglossum, angraecum, and a vanda.
They spend all winter on shelves in front of patio door windows, and
all summer on my back porch.
My question is when is a good point to move them outside? I live in
Pittsburgh, PA, and nights here are now mostly in the 50's, occasionally
in the high 40's. I know of course that different species have different
requirements here. I've put the masdevalias out already but none of the
rest yet. What I've read would seem to suggest that the cymbidiums could
also probably go out now, maybe I should wait another week or two on the
phals, and hold back the vanda and agraecum awhile later. I will
appreciate any suggestions from the amazing collective experience that you
all bring to this newsgroup.
Thanks,
Chuck Berlin