I love newbies to the local winter growing scene, they are so cute in their wonderment and surprise that we can grow through winter. Funny how we rarely consider how people lived through winter 200+ years ago before had canning, refrigeration and other modern conveniences we have enjoyed for the past 100 years or so. But obviously our species was growing and eating through winter or we would not be here today
Growing on the backside of the calendar has been going on for over 2 millennia
Some history from Wikipedia
The Roman gardeners used artificial methods (similar to the greenhouse system) of growing to have it available for his table every day of the year. Cucumbers were planted in wheeled carts which were put in the sun daily, then taken inside to keep them warm at night. The cucumbers were stored under frames or in cucumber houses glazed with either oiled cloth known as "specularia" or with sheets of selenite (a.k.a. lapis specularis), according to the description by Pliny the Elder.
The first modern greenhouses were built in Italy in the 13th century to house the exotic plants that explorers brought back from the tropics. They were originally called giardini botanici (botanical gardens). The concept of greenhouses soon spread to the NetherlandsEngland, along with the plants. Some of these early attempts required enormous amounts of work to close up at night or to winterize.
So you can see we have had winter growing for a long time. Read old gardening texts and they talk about cold frames, hot houses, using compost to heat an area. Not to mention, erecting walls around the garden and enclosing it thus making a micro climate. All these things have allowed people to grow where there is winter for a long time. Granted most the food consumed in winter back in the day was dried-meats, grains, legumes, herbs, fruits, etc.. but people also grew some greens to get fresh food in the diet when it was scarce.
People also foraged for early greens starting when the snows melt. Take a look at the ground right now where there is no snow in the northern hemisphere and you will see all sorts of edible shoots-dandelion, chicory, chickweed, henbit are all growing here on Boulder belt Eco-Farm. And that is what is growing with no protection. The weeds (and cultivated plants) inside the hoop houses are growing fast. And remember we do not heat our structures but the protection the sheets of plastic give is more than enough to allow spectacular early growth.
The article talks about growing spinach in a hoop house and you can do that but we have found that spinach is so cold hardy that it does not need all the protection. A medium weight row cover will also do the trick. We planted 10 beds of spinach last fall (October, I believe) and we have been harvesting it since January (weather permitting-if there was more than 6" snow covering the beds than we could not access it. But it was quite happy under its' snow mulch and just waiting for better harvest conditions). We also have been growing cold hardy crops in our hoop houses like arugula, raab, lettuce, leeks, beets and spring mix (which is a mix of lettuces and mild mustard greens this winter as well.
This will be our 14th year doing so. And we do not use any fancy techniques to do this. Simple hoop houses which are literally metal conduit hoops with UV stable 6 mil greenhouse poly pulled over top and the edges secured in trenches dug into the soil and than the edges covered with said soil. I suppose our ancestors in the 13th century would say we are using very high tech materials as they would certainly consider the 6 mil UV stable plastic sheeting to be extremely high tech. But in the 21st century not so much. Instead in our century we are amazed at winter growing.
We marvel at locally grown spinach in March, Spring Mix before spring and yet this was something our ancestors took for granted. We have so much to learn from them, especially if we want to return to a sustainable local/regional food system.