The best way to lengthen the growing season, and therefore the harvest, is to make use of either a cold frame or a greenhouse, or both. Of the two, a greenhouse is the better option because it is ultimately more useful. A cold frame is useful mainly for starting plants, though it can also be used for low-growing vegetables and fruits like lettuce and strawberries. A greenhouse should be tall enough for fully grown tomato plants, even when they are in raised beds. A greenhouse is not a hothouse. A hothouse is, of course, heated. That would be stepping up another level in expense and trouble, which for a home gardener with a ten by twelve foot greenhouse would make every tomato unnecessarily expensive. No, a simple and inexpensive home greenhouse is primarily useful for extending the growing season from summer into spring at the front end, and autumn at the back end.

Roger Cook of This Old House helped this Mississippi homeowner build an inexpensive backyard greenhouse. At the end, Mr. Cook tells the homeowner he should be able to grow vegetables year round in the greenhouse. Since the greenhouse will be unheated, year round use would be possible in Mississippi, most of which is in winter hardiness zone 8a. Use in your location may be limited to three seasons.

There are home greenhouse kits on the market, and a gardener could spend over 1,000 dollars for a nicely appointed one. The very cheap ones are not worth even their low price, and will cause you more trouble than they’re worth. The greenhouse depicted in the This Old House video here is a solid, utilitarian model that should cost less than 500 dollars. It won’t win any awards for looks, but that would probably present an obstacle only for homeowners association members. One suggestion to improve upon the construction method in the video would involve using weather stripping or batting between the plastic and the staples to distribute the force of the plastic against the staples, reducing the chances of the plastic tearing loose in the wind. 1/2 inch staples would hold everything well, and to reduce frustration a quality staple gun is a must. As with a tarpaulin or any other lightweight material used outdoors, the plastic needs to be stretched tight to lessen its movement in the wind. After all that work and expense, you can look forward to a longer tomato harvest season, and to tomatoes that don’t cost a small fortune. You may even save a few dollars over the long haul, though it might be a stretch to say you could pay off your mortgage early, the way Radiator Charlie of West Virginia did with his ‘Mortgage Lifter’ tomatoes back in the 1940s.
― Izzy