Brimfield, Mass. — Last December, when ''Jingle Bells'' filled the air and folks hereabouts were taking sleigh rides in the snow, Peter Field began preparing for spring - and sweet, vine-ripened tomatoes that sell wholesale at better than $1 a pound.
When most Northern gardeners are merely thinking of setting out tomatoes, farmer Field starts harvesting his.
To get that sort of early production, Mr. Field must sow his seed the week before Christmas and grow his crop in heated greenhouses. That much is standard practice for out-of-season production here in New England. Unique, or as yet unconventional, is his use of the grow-bag method of culture - and Mr. Field believes he has hit on something good.
Bag or pillow culture is catching on slowly in the United States. Mr. Field, a public accountant-turned-farmer, has found that the method is cost effective, producing high-quality, sweet-tasting fruit that is readily bought by restaurants.
Bag or pillow culture is a form of container growing. Each plastic bag, filled with a soilless growing medium, can be planted to a variety of crops simply by cutting a small hole in the bag and sowing the seed or setting out the plant. The bags, which can be made at home, are slit periodically along the side to allow for slow drainage of excess moisture.
To make a grow bag, simply fill a plastic garbage bag with a peat-vermiculite mixture. Or use commercial grow bags available from garden centers.
European horticulturists were the first to experiment with this type of culture. In the US much of the pioneering work came from Dr. Ray Sheldrake of Cornell University. Dr. Sheldrake, now retired, has overseen the introduction of Grace Horticultural Products' ''Plant 'n Bag,'' which Field uses in his greenhouses.
Advantages include even production. Every plant produces 20 to 25 pounds of fruit, in Mr. Field's experience, compared with soil-grown plants, where individual production can range from outstanding to poor. For most greenhouse producers, significant savings come from not having to sterilize the soil.
For individual gardeners, Mr. Field sees several advantages.
''You get an instant garden wherever the soil is unsuitable or nonexistent,'' he points out. Brick or stone patios or concreted backyards are readily converted to gardens this way.
Where tree roots encroach, the bags serve a double purpose. They isolate flower or vegetable production from tree-root competition while providing a moisture-preserving mulch for the trees. This option, of course, is only feasible where sun reaches the area in question.
Finally, they adapt readily to stand-up gardening situations. A simple but sturdy, waist-high framework of 2x4 lumber, covered with fencing wire at the top , makes an inexpensive support for grow bags.
Mr. Field sets two tomatoes in each Plant 'n Bag, which he says lasts two years. Ultimately he removes the planting mix and spreads it around his fruit trees as a mulch and soil conditioner. In other words, each bag yields 80 to 100 pounds of tomatoes before having to be disposed of as mulch.
Home gardeners using the bags for tomato production could put two plants in a bag, plus some low-growing parsley or sweet alyssum around the edge of the bag to dress it up.
The mix in the bag contains the necessary nutrients to get the plants off to a quick start. But for the growth to continue, the plants will have to be fed regularly, as with any other form of container growing.
Mr. Field uses an automatic drip-feed installation. The home gardener, however, could simply punch one or two feeding holes in each bag and apply the liquid fertilizer through a kitchen funnel once a week or once every other week.