While easy to maintain there is a bit of work that does need to be done.
Specifically, sweet basil, the popular variety of basil grown for use in the most sublime pesto sauces, is an annual. Generally, the end of summer or first part of fall heralds the end of season basil harvest, it is meant to live its life cycle within one year and thereafter go to seed. So basil’s growth cycle doesn't include overwintering; rather it dies down and the hard seeds wait in the ground over winter and then germinate during the spring thaw. When temperatures dip, basil suffers cold damage almost immediately in the form of blackened leaves. Therefore, basil and cold weather do not gibe so I do not even try.
Sage, Oregano, and Thyme
Now is the perfect time to cut away any dead or woody stems you find around the base of your sage, oregano and thyme plants. Also pull up any weeds you find, as they can overwinter and cause a big, overgrown mess next spring.
The most important chore for your sage, oregano and thyme plants would be to trim off the dead flower heads and to prune back just the top of the plant. Doing this will keep your plants bushy and healthy. Take caution not to trim the flower heads too low. A light snipping of the top-most leaves is usually plenty. You want these plants to have enough time to recover from the cutting before any really cold weather arrives. Drastic pruning and early first frosts are not a good combination.
Save the healthy, pruned-off leaves for drying. Simply string up the sprigs of leaves on a line somewhere in your house where it is relatively warm and dry. Keep them on the line until they are ready to crumble. At this point, you can store them in an airtight container and use them for culinary and medicinal purposes.
In most climates, sage, oregano and thyme will be perfectly fine left outside unprotected, even in the cold weather. However, if we get any of that very cold to extremely cold weather, you may want to pot a few of these plants and take them indoors or consider giving them extra protection in the herb garden. I lost a fair number of herbs a few years ago when we had an unusual December snowfall.
Mint & Lemon Balm
Mint and lemon balm are also perennials that will fade as the weather cools. Many gardeners and cooks like to pot up a little bit of mint to take indoors for wintertime use. This will work, but your mint may struggle indoors and become relatively straggly and unhappy.
You can store mint in the freezer. Harvest your mint, clean it, and then chop finely. Pack into ice cube containers, add water, and then freeze. Pull out cubes of “fresh mint” to thaw and use as needed.
In most of our areas, chives will thrive outside in the garden until the bitterest of winter cold arrives and even then it will probably be fine. That said, it’s still a wise idea to pot a little clump of chives to take indoors, just in case Old Man Winter decides to ruin your chive crop sooner than you were prepared for. When the serious cold temps do arrive, chives will go dormant until the weather begins to warm up in the spring. Then they just pick back up where they left off! Chives are not only healthy and delicious, but they are seriously one of the easiest herbs to grow. Give them a try if you have never grown them.
Chives are very hardy and can grow almost anywhere. A sunny kitchen windowsill will usually provide your chives enough light to keep them happy until they can be replanted outdoors. Water your chives on a regular basis, as they don’t like to be dry. But do not overwater them. If you’re a gardening purist, you can feed your chives with an organic fertilizer about once a month to keep them in tip-top shape while they are indoors.
If you don’t have an indoor sunny window, you may also consider placing a pot of chives on a back deck or covered porch where they are partially protected from the wind and bitter cold, yet still receive enough light to grow normally.
Rosemary is a robust and hearty herb, that is found all over the central Texas area, but it is still a Mediterranean plant that can succumb to cold temperatures. It will not survive outdoors in extremely cold weather. So if Jack Frost is at the windows you may want to cover your rosemary until the temperatures rise a bit.
To save rosemary over the winter in cold climates, most folks place the plant in a pot. About a month before the first frost is expected, bring the pot in to a protected area near the house, such as a covered porch or deck. When the temperature drops below 30 degrees, they take them inside to a garage or basement. Only bring them inside the house as a last resort. Look, I think that this is way too much work even for the folks in really, really cold climates. Afterall, your rosemary will fare better outdoors with fresh air than in the dry indoor heat. Rosemary loves light — so if you do have some in the house, make sure you place the pots near a window or door. Take the rosemary back outside as soon as the coldest part of winter has passed.
If you’d rather not fuss with your rosemary to this degree, you can always just leave it outside. I have had the same rosemary plant growing for the past seven years here at my Hays county home. If you are going to leave your rosemary outside in the dead of winter, consider covering it with a floating row cover or simply use a towel or blanket for protection when temps drop below 30 degrees, especially when the cold lasts more than a few days.
I have always had trouble growing lavender myself – you can’t have a green thumb for everything I suppose! Lavender plants will tolerate many growing conditions, but it does best in warm, well-drained soil and full sun. So, if you’re allowing your lavender to stay outside in the winter, you’ll need to provide it as much sun as possible.
It might surprise the herb gardener to know that dampness, more than cold, is the culprit responsible for killing most of their lavender plants in the winter. Wet roots during the cold season can be a real problem for those trying to grow lavender and keep it outside year-round. Protect your outdoor lavender plants with an extra layer of mulch this winter.
As you clean up and clear out your herb garden, you may find plenty of herbs for drying that you didn’t even realize you had. It’s a great time to practice your drying skills. Dried herbs are delicious to use in the winter kitchen as they offer a taste of spring and summer past. Dry them now to enjoy the flavor in the coming cooler months. They also make great holiday gifts!