You'll see this warning on many seed packets and plant tags: Plant after danger of frost has passed. It's sage advice any gardener would do well to keep in mind, which is why savvy planters wait until after the average last frost date to sow. Mother Nature, however, doesn't always play by the same rules so it pays to have backup plan to protect seedlings from the cold. In a pinch, a terra cotta pot can be turned into a frost guard. Upend an empty pot over delicate seedlings to save them from the chill, and remove it when temperatures rise to keep your plants growing.