Ohhh forgot to say that it's 39 degrees but feels like 32.
Roly, we'll see freezing temps in 6 hrs. Hopefully they will be short lived and not much harm to plants.
With the rain we've had, if it does get past 32*, a thin layer of ice on plants will protect them better than being dry. Orchids on the other hand, don't fare so well. Hopefully you've brought yours inside, or at least your favs.
This is something I go through every year as my nursery is not a traditional greenhouses but outside under shade cloth with winterizing plastic (thin plastic to break the wind). There are air leaks everywhere.
Last year it went to 28 degrees 8 times here so I have a lot of experience. I run the watering system on all the orchids when the temperature goes under 40. My well is a consistent 70 degrees.
I accept the possible damage in the winter for the better growth in the summer. Surprising there was minimal damage last year from all the water. Pythium fungus started (black rot) but as soon as I open the ends of the houses and let the cool (45 degree) air in the fungus stopped. It apparently dies under 50. My total losses for the winter was 10 Cattleya leaves cut off. (10,000 plants)
My new shadehouse did not have the watering system installed in time for this freeze. While I expected the house to be empty this winter it is totally filled. The Phal section under two layers of shade cloth is consistently at 38-39 degrees going to 80 when the sun shines. The Cattleya section under one layer of shade cloth is probably a few degrees colder.
I have 6 Phalaenopsis at the front of my house. It is open to the weather but there are tall bushes around them on three sides. They are my test plants and had no damage last year with 8 days of 28 degrees. I have Aerides and Spathoglottis growing under my oak tree and they got no extra protection.
It went to 26 last night. I do not expect any problems in the shade houses. Anyone wanting an update next week on the test plants outside just drop me a note.