1870'cold frame still in use

We have a stone structure(8'x 25')that was built in the 1870's that functions as a compost and cold frame. Every year we plant Plumbego auriculata in our urns(3).

This plant cannot tolerate our winters so I transfer the plants into the cold frame every November. I have 4 hard plastic doors that protect the plants from the cold. When we get warmer rainy winter day like today, I take off the doors to let the plants get some water. They look poor now, but in April, I will take them out, prune, and transplant to the urns. The cast iron urns were purchased in Italy in 1890, shipped to Mexico City, and then transferred by DONKEY CART to New Orleans, and then trained to Marietta. What a trek!