How to keep orchids warm safely in winter?

[Ray]

There are actually two issues (besides the cost of energy), providing the heat and holding onto it.

Lots of things can provide heat - seedling mats, heaters, lights, even fan motors - but just like water evaporating from a tray, the trick is confining it so it won’t get dispersed throughout the living area, where it will have a minuscule effect.

“Tenting” the plants with plastic sheet will trap the humidity and heat, but using some foam panels to “box” them will be even more effective.

I had an unheated basement in Pennsylvania. I built a “seedling nursery/intensive care unit” starting with a 1 x 2 meter plastic hydroponics ebb-&-flow table to which I added sides and a top made from 5 cm polystyrene insulation sheets. I fabricated sliding glass windows for the front for access.

It was illuminated by two Phillips commercial 35W horticultural LED strips, there were two “muffin fans” for air circulation, and there were two 15W seedling heat mats. In a 55F (12-13C) basement, when all were on, the chamber got into the upper-80’s (30-32C) if not higher. Overnight, the heat mats alone would maintain it at about 75F/24C, so unless I was trying to encourage rerooting, I cut back to only one mat to drop the temperature a bit.