Question: I had a wonderful herb garden this year. I grew lemon verbena, several types of basil, thyme, sage, chives, oreg-ano, lemon balm, lavender, lemon verbena and rosemary. Do they need any special treatment over the winter?
Answer: What a wonderful variety of herbs. Usually grown for cooking, they are also valued for cosmetics, perfumes, dyes, and medicinal purposes. They have a long history with man and have been used in every culture around the world. If cultivated properly many will survive in the garden for several years. Others may need a little extra care or be grown from seed each growing season.
Herbs can be divided into tender annuals, tender perennials, or hardy types. Tender annuals will be killed off with the first frost in the fall. They should then be removed from the garden bed to minimize overwintering insects and diseases. Some tender annuals can be dug up, potted and brought indoors. They will continue to produce for some time but may struggle throughout the winter. Careful inspection for insect infestations should be routinely done. This group includes basil, cardamon, coriander or cilantro, dill, and lemon grass.
Tender perennials in-clude lemon verbena, and rosemary. These herbs are marginally winter hardy and will not survive during a severe winter. They should be brought indoors to overwinter, under adequate light but even so some leaf drop may occur. Lemon verbena is a deciduous plant and will lose all of its leaves indoors. Rose-mary is a tender perennial that does not do well in a home environment without some extra consideration. Rosemary prefers a cool wet winter which is just the opposite of an indoor climate. If placed in a sunny cooler room and kept moderately moist its chances of success are greater. Heavily mulching your rosemary plant outdoors may be a simpler method.
Most other hardy herbs can stay in the garden and benefit from a two to three inch layer of mulch after the first hard freeze. This will help maintain uniform soil temperatures around the root zone and provide protection against heaving caused by alternating freezing and thawing of the soil. Hardy herbs include chives, lemon balm, bee balm, fennel, and most thymes.
Herbs should not be fertilized nor heavily pruned after early August. Late summer applications of fertilizer will promote growth that will not have time to harden off before cold temperatures arrive. Woody herbs should not be pruned four to six weeks before the first hard freeze. Woody herbs such as sage, lavender, and oregano fall into this category.
Mona Bawgus is a certified master gardener with Rutgers Cooperative Extension of Atlantic County. Write to her c/o Rutgers Cooperative Extension, 6260 Old Harding Highway, Mays Landing, NJ 08330.