Many years ago, we grew and sold a few acres worth of vine ripened tomatoes at the farmers' market. They are a great item to sell there because people will make a special shopping trip to buy them. With all of the technical advances made in trying to get a nice vine ripened tomato to the supermarket shelf, it just hasn't happened yet. There is nothing like a tomato that has been allowed to turn completely red-ripe while hanging on the vine. Once you pick it, you better use it in the next day or two, so as you can see, people need to and will go out of their way to buy vine ripened tomatoes. One observation we made when we first started selling tomatoes was that people at the farmers' market fell into the habit (or pattern might be a better term) of buying the same items from the same vendors each week. It didn't take long to come to the conclusion that being able to sell folks the first of the season, vine ripe tomatoes, would "lock-in" a customer base for the rest of the season. That prompted some research and what I found out back then was there was a system for early planting that could result in having tomatoes a few weeks earlier than having to wait until the frost danger had passed. It utilized black plastic to cover the bed the tomatoes were planted on, and then a clear plastic was put over the top to create a mini greenhouse to both protect against frost and provide warmth for early growth. The clear plastic was supported by heavy wire hoops, so the tunnel it formed was about a foot and a half over the plants. This gave them enough room to grow and not push up against the plastic until late April when the tunnels would be removed. By that time, the tomato plants would be almost two feet tall and be just about ready to start setting fruit. Compared to a field transplanted after the frost danger was over, these early tunneled ones were way far ahead.
Since all of the materials we used to use for this system were intended for commercial farms, it doesn't make sense to buy them. There would literally be enough plastic to last us more years than we will be able to tend a garden. In looking around at what would make good substitutes, we had all we needed already on hand. For the black plastic to cover the bed (and help keep the young root systems warm), we used a black plastic trash bag. Just use scissors and cut the side and bottom seams, and presto, you have a single sheet of black plastic to stretch out and cover the planting bed. As you can see in the picture of the bed, it's important to shape it so the sides are well defined. This lets you pull the plastic tight across the top to make sure the plastic contacts the soil underneath it for maximum root warming.
The next step is to plant the tomato plants and put something over them to support the clear plastic tunnel. If you look closely at the next picture, you see I have used fencing wire for the tunnel supports. Any type of heavy wire will work. It needs to be heavy enough so that a length around 80 inches can form a strong enough hoop to hold the clear plastic up over the plants. If the wire is too thin, the wind might push it around enough to collapse the tunnel. Once the wire is cut to about 80 inches, put it over the planted bed and stick each end of the wire in the ground at least 8 inches. This anchors it very firmly. The two plants you see in the picture are a Celebrity and an Early Girl. Both are very tasty when picked vine ripe! Also remember to cut the hole in the black plastic big enough so it won't touch the stem of the plants. I made the planting holes around 3 inches in diameter.
In the third picture, you can see the final assembled tunnel. The clear plastic we used here is just plain old 1 mil thick painters plastic. You can buy a small roll for a couple bucks at any big box hardware store. The clear plastic is stretched over the wire and its edges are buried with soil on one side. You can bury both sides if you want but I used bricks to hold down one side so I can lift the plastic up and put some other plants in the tunnel to make use of its warmth. There are some squash and basil seeds in Dixie cups in the tunnel right now. I figure by the time they have outgrown the Dixie cups, it will be warm enough to plant them somewhere else in the garden. The little rows of slits about a third of the way up the side of the tunnel are for ventilation. Believe it or not, when the sun shines on this set up, it gets hot in there to the point if could fry the young plants. With a few slits cut in with a razor, it allows enough heat to exit but still keep things nice and toasty under the tunnel.
As a matter of fact, this picture shows just how nice and toasty it gets in there. This thermometer is in Celsius, so I will give you the Fahrenheit value. It's about 100 degrees in the tunnel this afternoon. If you want to do the conversion yourself, it goes like this: 38 x 9=342. Divide that by 5 and you have 68.4. Now add 32 to it and the Fahrenheit value is 100.4! That's a pretty good solar gain since the outside temperature was in the high 60s. And remember, this set up can be done with materials most people already have on hand. It's a great way to get a jump on the season and have good old fashioned tomatoes in time for a Fathers' Day BBQ!
