"Wintering over" is the official term for tucking perennial herbs in for the season. Cleaning them up and making them cozy for the cold months ahead will encourage them to be healthy and tasty when they reappear in the spring.
First make sure that all the annuals, those herbs that need replanting in the spring, are removed, roots and all. These include basil, borage, scented geraniums, parsley, lemon verbena and cilantro. You can dry or freeze any tender leaves, and chop the stems up to add to the compost heap.
Once the annuals are out of the way, take a good look at each perennial in terms of trimming it back to a tidy winter length. For years, the trimming rule was to cut back spring-blooming herbs in the fall, and summer-blooming herbs in the spring. But trimming back all herbs in the fall has genuine advantages. It gives herbs a fresh start in the spring, plus fall trimming eliminates dead growth that can cause herbs to rot and attract harmful insects.
Trim herbs to their natural shape. For instance, trim sage into bushy mounds. The same goes for thyme, tarragon, oregano, marjoram, the mints, the balms, hyssop, germander, lavender, santolina and southernwood. Hearty growers, like the mints, chives and bee balm, can be thinned out by using a trowel or shovel to dig out clumps of the plant, roots and all. Replant the clumps elsewhere in your garden, or share them with friends. And if you want to move an herb from one location of the garden to another, this is the time to do it.
Always use sharp pruners for trimming, because clean cuts are less traumatic to the herbs. If you don't have pruners use sharp kitchen shears or the sharpest scissors you have in the house. Be sure to remove any damaged or dead branches but don't trim healthy growth any shorter than six inches.
Apart from trimming, certain herbs fare better with a bit of special care. Lavender, for one, doesn't like wet feet, so dig in some vermiculite or perlite around the base. It's also prone to heaving, which means the entire root ball can give a heave-ho right out of the soil. Mulch around the base of lavender with pine needles to avoid this problem. Along with lavender, other gray-leafed herbs like silver santolina and silver thyme can be more tender than their greener cousins. One way to give them extra winter protection is to gently cover them with evergreen boughs, if available. These covers are especially helpful if the gray-leafed herbs are exposed to north winds.
If you have window space with at least four hours of sun a day, you can bring potted herbs in for the winter. First trim them, and if they're not already in pots, use a trowel to dig them up and ease them in. Then there's a little trick to get rid of any unwelcome critters living in and around the herbs: Keeping the potted herbs outside, make a tight tent over them with plastic dry cleaning bags. Set some non-toxic pest strips inside the tent. Let everything sit (out of the sun) and after about a week, the herbs should be bug-free. Try this with sage, lemon thyme and particularly rosemary, if you have had trouble wintering over this herb in the past.
Getting back to the herbs outside, a good tip on keeping herbs healthy can be learned from organic farmers. This time of year they add nitrogen to their soil by planting a legume-type cover crop, which automatically sends out extra nutrients. No herb garden is too small to do this, plus, it's easy. Just get some alfalfa, rye or buckwheat seed at a garden supply house, toss it on the soil around the herbs, then cover with a bit more soil. As the little plants grow they fill the soil with the nitrogen that herbs need. The cover crop dies before spring, no fuss or harvesting necessary.
If you're wondering what your neighbors might think of you growing alfalfa, just wait until they see you out watering your herb garden in the middle of winter. That's what you'll need to do if the ground becomes too dry. You'll also need to check each herb from time to time, trimming away dead branches and rearranging pine mulch and evergreen covers. And if your herbs have a southern exposure, you can even do some winter harvesting. Sage, for instance, can stay green through mid-December, and the smaller leaves are tasty for saute's and in poultry stuffing. Chives can remain green through February, jazzing up winter stews and breads.
Then before you know it, usually in March, the first tiny leaves of the balms and mints peek out around the bases of the plants. Pick them for adding to green salads and keep a daily eye out for other shoots and slips to munch. As each herb awakens for the new season, you'll be glad you lovingly tucked it in this fall.
Judith Benn Hurley is the author of Garden-Fresh Cooking (Rodale Press).