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As swimming pool contractors during the 1960's we found ourselves installing enclosures to extend the swimming season here in the state of Wisconsin. The configuration of the structures was similar to a Quonset hut - a continual arch from base to peak - and the materials were aluminum and fiberglass. Solar radiation heated the water in the pool as well as the air in the enclosure so effectively that the season for swimming was actually doubled!
This experience led to a search for lower cost materials
to enclose a swimming area and we soon developed an aluminum framework over
which was draped a poly vinyl chloride (PVC) clear covering. The cover was cut
and heat sealed to make a perfect fit over the framework.
In
fall of 1974 we began season extension studies in the field of
horticulture. An ordinary swimming pool dome was installed on a low wooden base
constructed around an existing garden. The sun's radiation energy heated the
ground so effectively we were able to begin planting (in Wisconsin) in early
February. Our "walk-in cold frame" differs from a greenhouse in that
the ground is our heat storage source. Heat accumulated throughout the day is
released throughout the night from the ground, providing significantly enhanced
protection from killing frost.
We discovered that the northern climes can expect to experience three
distinct growing seasons with a covered garden. Each season is of sufficient
length to be able to produce 90-100 days. The early season - spring - will produce vegetables of
outstanding, almost unbelievable quality. They will be insect and disease free
without any chemical control. There are few weed problems. By covering the
garden an otherwise unproductive season becomes highly productive - totally by
using solar energy.
The
mid season - summer- is the least desirable of the
three. Vine crops do well, but salads are generally of lower quality this time
of the year. We are subjected to heat, drought, weeds, pests, and diseases
during the summer.
The late season - fall - is similar to the spring
season. Vegetables are once again excellent.
Gardening techniques such as inter-planting and high density planting are very adaptable. The more we increase productivity and efficient space utilization the less space there is for weeds!
A plot of 450 square feet in area can produce enough high quality fresh vegetables to feed a family of six for at least nine months of the year in a northern climate!
