Late spring freezes can wreak havoc on fruit trees or tender plants such as flowers and herbs. When you are trying to protect just a small patch of backyard fruit trees, there are some quick and inexpensive ways to do so. The key is to keep as much heat as possible near the fruit trees, and to deter the roots from freezing as a result of the cold air.
Lay out large black trash bags on the floor, and secure them together with duct tape. Make a second layer of the taped-together trash bags of the same size and lay the two sheets on top of one another, lining up the edges.
Tape together all sides but the bottom, overlapping the edges a little bit. This will create a tent for each fruit tree.
Water the area around the trees during the hottest part of the day before a freeze. The moisture will rise up throughout the evening to warm and insulate the tree.
Fill large plastic gallon jugs or pitchers with hot water, with 1 inch between the top and the surface of the water. These will release heat throughout the night around the fruit trees to keep the temperature a little warmer. Place these around the base of the tree.
Cover each fruit tree with the plastic garbage bag tent by sliding the open end over each tree and pulling the plastic down securely around the tree, down to the ground. The water jugs should be inside the plastic.
Hold the plastic bag edges down with firelogs, large rocks, etc. Make sure there are no gaps around the bottom of the plastic.