When a late spring frost is predicted for your area, you'll want to take steps to protect your tomato seedlings. Moisture in the air can settle on the leaves of unprotected plants and freeze them. If the tender leaves of seedling tomato plants freeze, they will turn dark green or black in color and become limp or sludge-like. A tomato plant cannot recover from this type of attack, so it’s important to know how to keep tomato plants from freezing. You can protect them using some basic household items.
Collect gallon-size milk jugs until you have one for each tomato plant. Asking friends or family members to save them will help you collect them faster.
Rinse the inside of each jug to remove any residual milk. Cut off the bottom of each jug with a sharp knife, straight across the base of the jug.
Set a jug over each plant in the evening and press it down into the soil an inch or two to help hold it in place. Pack the displaced dirt around the base of the jug to secure it.
Remove the jugs in the morning so your plants can receive air and light. Store and reuse the jugs as needed whenever frost is in your forecast.
Row or Bed Coverings
Place wooden stakes at each corner of the row or bed area and push them into the ground about 6 inches. Place more stakes or sticks every 2 feet along each side from corner to corner.
Drape the bed sheets over the stakes so the entire bed or row is covered and the sheets touch the ground all around the outside of the row or bed.
Set rocks or bricks on the outer edges of the sheets where they touch the ground to help anchor them in place and keep the sheets from sagging over the tomato plants in the middle of the row or bed.
Remove the sheets in the morning to allow your tomatoes fresh air and sunlight. You can leave the stakes in place, if desired, just in case another frost threatens.