Nothing damages the herb garden like a spring frost. The shock of ice crystals in the tender leaves will kill a plant quicker than a rabbit nibbling on the shoots. A good mulching in the fall should have protected the herbs in the garden from the spring frost damage but there are other steps you can take to ensure a healthy crop of herbs throughout the growing season.
Section off the plants you want to prevent frost damage to in the herb garden. If the entire bed is planted with herbs this should be easy to do. If not, you will need to tend to each plant.
Cover the herb garden with the plastic so no cold air can get in to the delicate plants. Weigh the plastic down with cinder blocks or garden stones.
Place buckets on herb plants that are not located in the regular garden or are in flower beds. A rock or other stone will keep the bucket in place overnight.
Drape sheets over larger groups of herbs. The sheets also work well when placed over an entire herb garden. Anchor the sheet with rocks or cinder blocks.
Remove the coverings when the sun is out and the area covered is no longer in the shade. It is fine to leave the covering on for a while as the added warmth helps to keep the plants growing.