Tomatoes produce abundant fruits when grown in warm climates where temperatures remain above 50 degrees Fahrenheit during the overnight hours. For northern gardeners, this may pose a bit of a challenge, as nighttime temperatures often dip into the 50s well into the summer. Keeping tomato plants warm and protecting them from the stress associated with cool temperatures requires an insulated barrier between the plants and the nighttime air. Commercial water-filled plastic "wells" that surround the plants are effective, but often expensive. Making your own with recycled materials saves money and provides warmth and protection for your tomato plants.
Wash and dry five to seven 2-liter bottles for each tomato plant. Small seedlings need for five or six, while larger plants require seven. Fill the bottles with water and replace the cap.
Arrange the water-filled bottles around the base of the tomato plant to form a circle, allowing several inches between the foliage and the bottle. Bottles should touch, with no gaps between them, to form a solid barrier against the elements.
Secure the bottles in the soil by mounding soil around their bases. Tie a length of garden rope or twine around the circle of bottles to secure in place and prevent them from toppling in the wind.
Cover the top of the circle with plastic at night if the tomato foliage grows close to the top of the bottles; if not, the bottles will provide enough protection to prevent damage from frost. The bottles heat during the day and slowly release heat during the night, providing gentle heat for tomato plants and protecting them from chilling temperatures.
Remove bottles once seedlings have grown above the top of the bottles and temperatures remain above 50 degrees at night.