Winterizing the herb garden

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If treated properly, many herb plants will survive in the garden for a number of years. Others are sensitive to frost or severe cold weather and must be brought indoors, protected, or replanted each year. Annual herbs will be killed with the first hard frost in the fall. Remove dead plants in order to minimize overwintering insects and disease problems. Some frost sensitive herbs, such as basil and geranium, can be brought indoors for the winter. Take cuttings to root or pot the entire plant.

Many perennial herbs are winter hardy in all or parts of North Carolina and can be left in the garden. A few plants are marginally winter hardy; in a mild winter they survive but may die during a severe winter. They can be brought indoors to overwinter. Unless they receive adequate light indoors they may drop some of their leaves. Lemon verbena is a deciduous plant; it will lose all of its leaves indoors.

After a severe winter, some outdoor plants such as rue, sage, thyme, and southernwood, may appear brown and dead. The leaves may simply be dehydrated or the plant may be dead almost to the ground. Scrape the bark of a few stems to determine the extent of damage. If the stem is green, delay pruning until after new growth begins. Additional information on winter hardiness of specific herbs can be found in the table.

Normally hardy in: M = Mountains, P = Piedmont, C= Coastal Plain

Common Name	Scientific Name	Hardy	Comments
Angelica	Angelica archangelica	M, P, C
Artemisia	Artemisia spp	M, P, C	good drainage
Basil	Ocimum basilicum	--	Tender annual
Bee balm	Monarda spp	M, P, C
Caraway	Carum carvi	M, P, C	Biennial; lightly mulch
Cardamon	Elettaria cardamomum	---	Tender annual
Chamomile	Chamaemelum nobile	M, P, C	Lightly mulch; wind protection
Chives	Allium schoemoprasum	M, P, C	Lightly mulch
Comfrey	Symphytum uplandicum	M, P, C	Lightly mulch
Coriander (cilantro)	Coriandrum sativum	---	Tender annual
Costmary	Chrysanthemum balsamita	M, P, C	Lightly mulch
Dill	Anethum graveolens	---	Tender annual
Echinacea	Echinacea purpurea	M, P, C
Fennel	Foeniculum vulgare	M, P, C
Feverfew	Chrysanthemum parthenium	M, P, C	Lightly mulch
Garlic	Allium sativu	M, P,C	Plant cloves in fall; lightly mulch
Garlic chives	Allium tuberosum	M, P, C
Garlic, elephant	Allium ampeloprasum	M, P, C	Plant cloves in fall; lightly mulch
Geranium	Pelargonium spp	--	Tender annual; bring indoors
Lemongrass	Cymbopogon citrantus	--	Tender annual
Hops	Humulus Iupulus	M, P, C
Horehound	Marrubium vulgare	M, P, C	Lightly mulch
Hyssop	Hyssopus officinalus	C	Tender perennial
Lavender	Lavendula angustifolia	M, P, C	Hardiness varies with cultivar;
Lemon balm	Melissa officinalis	M, P, C	Lightly mulch
Lemon verbena	Akitsua truogtkka	C	Tender perennial;
Marjoram	Origanum majorana	C	Tender perennial;
Mints	Mentha spp	M, P, C	Lightly mulch; wind protection
Oregano	Origanum spp	M, P, C	Hardiness varies with species
Parsley	Petroselunum crispum	---	Biennial; treat as annual
Pennyroyal	Mentha pulegium	P, C	Provide wind protection
Rosemary	Rosmarianum officinalis	P, C	Tender perennial;
Sage	Salvia officinalis	M, P, C	Lightly mulch; wind protection
Sweet cicely	Myrrhis odorate	M, P, C
Tansy	Tanacetum vulgare	M, P, C	Lightly mulch
Tarragon	Artemisia dracunculus	M, P, C	wind protection; good drainage
Thyme	Thymus vulgaris	M, P, C	Hardiness varies with cultivar;
Valerian	Valeriana officinalis	M, P, C	Lightly mulch
Verascum	Verebascum spp	M, P, C

Improving Winter Survival - Most herbs benefit from a 2- to 3-inch layer of organic mulch during the growing season. Mulch is an adequate winter protection for herbs such as mint, chives, and fennel providing protection to minus 20 F. Rosemary, lemon verbena, and a few other perennial herbs are not reliably winter hardy. Extra winter protection can be provided by cutting plants back to within a couple inches of the ground after the first hard frost and covering the remaining stub with soil. Then cover the soil with a 4- to 5-inch layer of mulch. For lemon verbena, the use of a microfoam ground cover (the packing material used around fragile items) also works held down with soil works very well providing over 95% survival in most years. An alternative method is to encircle the plant with a cage of hardware cloth or chicken wire. The cage diameter should be about 12 inches larger than the plant (6 inches on each side). Fill the cage with mulch. Herbs should not be fertilized after early August. Avoid significant pruning (light harvesting is acceptable) in August which will stimulate new growth. Also, avoid severe pruning in late fall since winter hardiness is reduced until the cuts have healed. Woody plants should not be severely pruned within 4 to 6 weeks of the first severe freeze. Excessively wet soil or sites with standing water can decrease winter hardiness of some plants. Keep plants adequately watered during late summer and fall. Drought stressed plants are weaker and are often less cold hardy. Water during a dry winter, especially before a severe freeze. This is especially true for evergreen plants that will lose water from their foliage on bright, sunny days even when the ground is frozen.

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