In order to get an
early start on some cold-tolerant crops, I installed a simple hoop bed.
It is simply bent plastic tubes that I found covered by a sheet of
plastic that I bought. I erected the hoop bed two weeks before planting
in the soil in order to give the bed time to dry out. It rains so much
in Portland that the soil often gets water-logged in the rainy months.
After two weeks of drying, I planted arugula, spinach and ruby chard, which are all cold-tolerant varieties, will grow throughout the long spring. On the rare sunny days, I open up the bed and give the plants some much needed direct sunlight. The plastic still lets UV light through, but does not provide the same solar energy as direct sunlight.
The plastic also keeps moisture in, so the beds practically never have
to be watered. Only on hot and sunny days do the beds begin to dry out a
little. One trick is to put a bucket of water inside the hoop bed so
that it stays wet even on hotter days. 