Start seeds of herbs perennial to your region in the late summer or early fall, at least eight weeks before the first frost, when it is still warm enough to encourage germination and allow the roots to become established before the coldest part of the year sets in. Transplants will need at least six weeks. To know what herbs to grow in your locale, first learn about your climate. After you know what temperature extremes and patterns your area has, finding suitable herbs to grow is easy.
Learning About Your Climate
The most standard reference available to U.S. gardeners is the USDA Plant Hardiness Zone Map. The most valuable piece of information it provides is the expected lowest temperature throughout the year. Many plants will die if they go below a certain cold threshold. Some can't even tolerate freezing temperatures, whereas others can be iced in a heavy frost and still recover. Another valuable resource is a weather website that carries historical data with temperature and precipitation averages for your region, like Intellicast.com. Knowing late summer and fall temperatures will allow gardeners to more accurately pinpoint how soon to start new plants before the first frost comes.
Year-Round Herbs Below Zone 5
Zone 3 dips to as low as -45 degrees F, and Zone 4 only rises 10 degrees beyond that, yet a few hardy herbs can take that kind of beating and still smile again by spring. This is by no means an exhaustive list, but here are a few that can survive in Zone 3: borage, chamomile (which also withstands light traffic), chicory, chives (which also likes acid soils), horseradish, lovage and tarragon. Zone 4-hardy herbs include: caraway, dill, garlic, anise hyssop, mustard greens, oregano and sage.
Year-Round Herbs in Zones 5-6
Creeping down to -20 degrees F and -10 degrees F respectively is still warm enough weather to sustain all the herbs above, plus a few more. The following plants can take Zone 5 conditions: fennel, Good King Henry, lavender, lemon balm, marshmallow, mint, Welsh and tree onions and wild strawberry. In Zone 6, you'll find English mace, honeysuckle and parsley.
Year-Round Herbs in Zones 7-8
Thyme is hardy in Zone 7 temperatures that dip as low as 0 degrees F. Once it warms up to the low of 10 degrees F in Zone 8, these other herbs appear: cardamom, jasmine, lemon verbena, licorice and rosemary.
Year-Round Herbs in Warm Climates
In Zone 9, plants won't experience anything worse than a light frost. In this zone, you'll find the following herbs: angelica, amaranth, bay leaf, celery leaf, coriander, ginger, lemongrass, marjoram, oregano, shiso and turmeric.
Aloe vera and Balm of Gilead can't take any frost at all. They insist on Zone 10 climates, which is why aloe is a regular resident in sunny windowsills, protected from the elements.