How to overwinter herbs? This is a difficult question because herb plants vary widely in their cold hardiness. Some perennial herbs will survive very cold winters with minimal protection, while tender perennials may not survive the first hard frost. If you’re concerned about winterizing your herb garden, the first step is to use your favorite Internet search engine and determine your plant’s cold hardiness, and be sure you know your USDA growing zone. Armed with that basic information, you can easily learn how to overwinter herbs.
Winterize Home Herb Gardens
Below are some general steps you can take in preparing herbs for winter.
Fertilizer – Never fertilize your herb garden after August. Fertilizing herbs late in the season will encourage tender new growth that may not survive the winter.
Watering – Water plants throughout late summer and autumn, as drought-stressed plants are more susceptible to cold weather damage. If the winter is dry, the plants benefit from an occasional irrigation (when the ground isn’t frozen).
Overwintering herbs that are perennial – Many perennial herbs are winter hardy. Some of these include:
In most climates, these plants just need a good pruning – down to a height of 4 to 6 inches (10-15 cm.), after the first few hard freezes. However, even sturdy plants benefit from a layer of mulch in climates below USDA plant hardiness zone 5. Apply a 3 to 6 inch (7.5-15 cm.) layer of mulch, such as chopped leaves, straw, pine needles, or bark mulch, but don’t apply the mulch until after the first hard freeze because you may damage the plant. Be sure to remove the mulch shortly after new growth appears in spring.
Some perennial herbs, such as rosemary, bay laurel, and lemon verbena, need a little extra help during the winter months. Cut the plants nearly to the ground after the first hard frost, then cover the plants with soil and top the soil with 4 to 6 inches (10-15 cm.) of mulch. A layer of evergreen boughs will also protect perennial herbs from harsh, drying winds.
Overwintering tender perennials or annual herbs – Some perennials may not survive cold winters, depending on your particular growing zone. For example, rosemary tolerates winters in USDA hardiness zone 7, and possibly zone 6 with good protection. Rosemary is relatively difficult to grow indoors, but you might want to pot it up and give it a try. Rosemary needs cool temperatures, bright sunlight and soil kept lightly moist.
Annual herbs, such as dill and coriander, survive for a single season and will be killed with the first frost. There isn’t much you can do about this, but be sure to pull the dead herbs and clear the area of plant debris. Otherwise, you’re providing a handy hiding place for pests that will make an appearance in spring.
Overwintering herbs indoors – If you’re concerned that your tender perennial herbs may not survive the winter, or if you want to continue using annual herbs year round, many herbs do well indoors. For example, you can pot up herbs like parsley or basil in autumn, then move them back outdoors in spring. Some container herbs can also be given winter protection outside.