A tree aloe with a frozen flower stem.
I knew it was coming. Everyone who owns a greenhouse in a cold weather area experiences this.
It was inevitable, but finally happened. I awoke Friday morning to outside temperatures at 16 degrees F, and as I fumbled in the dark kitchen for the coffee pot, I glanced, as I always do, with one eye open, through the porch window across towards the greenhouse just to see if the unthinkable happened. I usually see a puff of steam coming from the exhaust of the furnace near the roof, and even through the whole glass structure is frosted over, the corner near the furnace is always clear and melted near the peak. But not today. The entire house was silent and frosted over, and I knew what had happened. 
My fear was that everything would turn to mush, and thousands of dollars worth of collections would be lost forever.
sometime over the night, the furnace konked out from a lack of fuel. I knew that the previous sunday, while putting up holiday lights, that the fuel tank said 20%, blah blah blah, the work week flew by, and everytime I call the gas company they yell at me anyway for calling them too early. That will never stop me again.
Joe flew out to see what the damage was, ( and to sneak a cigarette), he came running in saying that the temp inside the house was near 31, and that we might still have time to call the gas company. He warned me though no to go look since the oxalis collections we’re frozen solid, as we’re many things. I knew that the sun would be up in an hour and was too shocked and depressed to go out to see. I sat and drank coffee staring at the road looking for the gas truck.
Long story short, the sun enver came out, it started snowing, gas truck game, re-primed the pump, the head came on with a whoosh and steam clouds once again rose through the falling snow. I then stepped out to see the damage, which, surprisingly was minor. Plants are so tough sometimes. I knew that I read somewhere that if kept dry, that plants could handle below freezing temperatures, and clearly, this worked. Besides the fact that most of my plants are cool- growing anyway, I did loose most of the pelargoniums, a couple tropical vines, some succulent bonsai and most tragically, the huge flower stem emerging from a tree aloe which I brought back from California, due to bloom for the first time this winter. Surprisingly, the velthiemias, Boophanes, Fresia, Cyrtanthus and Oxalis which where not only transparent and frozen hard, but wilted as if dead to the world, all recocoverd as if nothing happened! The cyclamen, narcissus collections all survived and may have even enjoyed the excitement. That said, the back-up heaters are now ready to run with gas and electricity, and even though I was complaining last week that the greenhouse was a burdon, another dependant keeping me from moving to another job, career, or excuse du jour, I am thankful that it is still there, collections and all.
Temps out side the house we’re 16 degrees F. This Agave paryii survives outside since it is well drained.
Matt,
For more than 20 years this was my greatest fear as I tended an instructional greenhouse at a major university. My greatest relief in my recent retirement is that I can “enjoy” the cold a bit more.
The fact that the sun did not come out may have been quite a blessing. Generally it has been found that the biggest amount of damage from freezing in plants occurs when the sun jump starts the metabolism of the plants right after dawn. You might have tried to run water over the plants to protect them and slowly warm them up. This is done in some commercial vegetable growing to protect crops.
Also you were lucky that the water pipes didn’t freeze. They can actually break & twist from the force and flail about wildly breaking lots of other things. I’ve actually seen this. It’s so dramatic it made the front page of the paper…