Whether cold weather threatens your tomatoes in the beginning of the growing season or the end, protect your tender tomato plants from overnight frosts or you will lose your tomatoes. Watch the forecast each day, and prepare for freezing temperatures to protect your tomato plants. Cover tomato plants with plastic sheeting, tenting it over the plants with stakes. This thin insulation will shield tomato plants from a light frost.
Pound the stakes into the ground at intervals around your tomato plants. If you are only protecting one or two plants, you only need one or two stakes. If you are protecting a large tomato patch, place stakes 4 feet apart around the perimeter and place additional stakes in the center area (also 4 to 5 feet apart). Use the hammer to pound the stakes approximately 4 to 6 inches into the ground.
Stretch the plastic tarp over the tomato plants, with the stakes holding the tarp up and off the plants. The plastic must not touch the tomato plants, because foliage that touches the plastic will freeze. Create a pocket of warm air above the tomato plants by suspending the plastic above the plants.
Extend the tarp down to the ground around the tomato plants and secure it with bricks or large rocks.
Remove the plastic tarp the next morning when the temperature rises above 40 degrees F.