Plant Covers For Cold Weather Diy . There are some varieties that are bred hardier than others, making them better options for cold environments. Watering the ground in the afternoon helps to protect plants from frost. Pin by Brenda Turner on Allotment Vegetable garden design, Cold frame from www.pinterest.com.au Simply place the milk jug over the plant, then mound mulch. Thinner covers typically protect plants to 28 degrees and permit 70 percent of sunlight to reach plants, while thicker covers protect plants from 24 to 26 degrees and allow 30 percent of sunlight to reach plants. Connect the 2x4s legs at the top with carriage bolts.