Category Archives: greenhouses

Building a Cold Frame

Building a cold frame was last weekend’s project at our house and we did it in the nick of time, just before the cold blast of arctic air and many inches of snow hit us this week.

Although we built a winter greens hoop garden a few years ago and it is working to produce winter greens like a charm (see my post about that here), my goal was to do a fall gardening project using the salvaged glass I’d saved years ago to make a cold frame.

Being in town, unfortunately, our neighbor to the south has a lot full of huge overgrown trees which shade our house in the wintertime, therefore my chosen “best” spot site for this mini-greenhouse isn’t perfect, but will get a few hours a day of sunlight on sunny winter days. The spot happens to be sandwiched between the concrete driveway and the house.

First, we took a trip to a neighbor’s dumpster where they are deconstructing part of a house and picked up a couple pieces of wood there, and then, we headed to our fabulous Boulder Resource Center (recycled community materials) to look around. It was a lucky day there, because we found three perfect sized lengths of redwood which ended up being exactly what we needed for the project.

The first photo, below, shows the project in its early stages. Designing the box with the materials at hand was the hardest part and I took a great deal of care and time in the planning stage. To construct it, my husband did the sawing and I got to have fun using the electric screwdriver.

This photo shows the project farther along, with glass in place. Careful measuring has paid off nicely.

Finally, the box is in place. Since this photo was taken, I’ve sunk it’s edges into the ground, found an old thermometer to put inside, and started a few spinach seeds as an experiment. I stacked rows of bricks against the back wall and plan to place a few old milk cartons inside that are filled with water as additional heat sinks. The floor is already covered in small rocks which should also help retain heat for this passive solar mini-greenhouse.

It seems to be pretty well settled that the plastic hoop house works best for growing winter greens in our area and if you think about it, glass conducts cold a lot better than plastic does. Eliot Coleman layers plastic with success in Maine’s cold winters. My project is an experiment and I hope to try a few things but mostly I want it for starting seeds next spring. I already think I should have made it taller so it could house some short tomatoes, but I will work with what I have. The glass panes slide apart nicely to vent it when it gets too hot inside and I will either bring the cold-sensitive seed starts indoors or throw a blanket over the frame on the colder spring nights.

Whew. Got it finished just in time. The total cost was about six bucks for this salvaged-materials project.

NOTE: As I post this, the outdoor temperature is 27F and the cold frame’s thermometer is showing 85F after the sun hit it an hour ago. Later… 100. Wow.

Also recommended, this previous post: Extend Your Growing Season with Simple Backyard Coldframes or Hoop Gardens.

Largest LED Vegetable Growing Factory in the World Opened in Japan in 2014

After the Great Earthquake that Japan experienced in 2011, it has repurposed a Sony Corporation semiconductor factory located in the northeast region’s Miyagi Prefecture and turned it into the world’s largest indoor farm illuminated by LEDs. General Electric reports that they developed the LED fixtures which emit light at wavelengths optimal for plant growth used in the indoor farm.

Another company involved in the project, Mirai Co., based in Tokyo, runs vegetable growing factories. This new growing indoor plant operation is on about 2,300 square meters of land and is able to produce 10,000 heads of lettuce plus other vegetables per day. The produce will be sold to local supermarkets.

The hope is to build more factories similar to this one in other parts of Japan. The LED lights reduce electricity consumption by 40 percent as compared to fluorescent lighting and can use spectrum specific light for optimal growing of the vegetables.

The combined venture further intends to export produce to other nations as well as export the entire growing factory set ups and technology. They have already received requests to do so.

For further information see: