Spring is here, in my basement. Allow me to set the scene. My basement is barely heated and I replaced what once was a south-facing Bilco door with a wooden frame supporting two clear polycarbonate panels. Plants that need light and tolerate or need a winter cold period, down to near freezing, have their wishes fulfilled out there in that old Bilco entranceway.
Temperatures are more moderate there than outdoors, generally warmer except later in spring when the basement’s mass of concrete keeps things cooler than hot, sunny days outdoors. Through winter, though, the non-frigid temperatures kept pots of Welsh onions, pansies, oregano, kumquat seedlings, hellebore, olive, pineapple guavas, and bay laurel green and happy. It’s cool Mediterranean climate down there, in winter, at least.