After a couple of snow days, the mini greenhouse supported by the flex plastic pipe collapsed because of the snow load. On the other hand, another mini greenhouse supported by platic electrical conduit still stands. So my experiment has proved that the flex plastic pipe is good for summer use while the electrical conduit can be used in all 4 seaons. The electrical conduit costs a little bit more and is harder to bend.
The veggies we try to grow is lettuce, spinach and choy sum. It looks like under this cold weather without any heat source, the growth is very slow but the plants survive.