It has been a surprisingly mild fall this year which was good for extending the gardening season. But sooner or later the winter cold will come and anything left without the protection of a cold frame will be frozen. But don't worry, when that time comes, there are a variety of plants that you can bring indoors to keep your inner gardener happy and keep you supplied with fresh herbs.
If you live in a well-insulated home that is usually kept at a reasonable temperature (ideally above 60 degrees) throughout the winter, then the easiest strategy for growing herbs indoors is to bring in already mature plants and place them on a sun-filled, south-facing windowsill for maximum sun exposure. Don't let your plants touch the cold glass of the window. If you don't have a sun-filled, south-facing window, then your other option is to invest in grow lights.
Don't start from seed
Starting plants from seed or seedlings in the late fall is also possible, but you are unlikely to succeed without the aid of grow lights. In addition, while indoor herbs will survive during the winter, don't expect them to actually grow very much unless you supplement their light exposure with grow lights.
Use mature herbs
Bring your outdoor, potted plants indoors when the weather gets cold. Ideally you should get your plants adjusted to the indoor environment by bringing them indoors for increasingly longer periods of time over a couple weeks, and then move them inside before the first frosts. However, since this probably takes more time and effort than most people are willing to dedicate, you can also just bring your plants indoors all at once after a warm spell and hope for the best.
Believe me, plant pests appreciate a warm windowsill just like your plants do, and they'll be happy to sit there and eat your plants before you do. Therefore, check your plants for pests when you bring them indoors. If you notice any, you'll want to get rid of them. There are organic as well as conventional methods for doing so. When it comes to organic versus conventional pesticides, remember that you plan on eating these herbs.
Keep in mind that your plants will receive less light indoors than outdoors. This might cause them to adjust their growing strategy. For instance, don't fret if your plants drop some of their older leaves. They're going to grow new, smaller leaves that will be better able to deal with the lower light levels.
The same dry indoor winter air that makes your hands chapped will dry your plants' soil, especially if they are in small containers. Be sure to check the soil regularly and water well when it is dry, but don't water more often than you need to, otherwise you may encourage root rot. You can increase humidity by misting your plants or using a humidifier.
Since indoor wintertime conditions don't permit significant growth, you should use a very reduced amount of fertilizer or no fertilizer at all.
Good indoor herbs
Try to select dwarf or compact varieties of common perennial herbs like rosemary, oregano, thyme, marjoram and sage. They should be able to last the winter and be put outside again after the last frosts. Annuals like dill and basil, if brought in already mature, will last one or two months but they will fade away eventually as all annuals do. Again, don't expect too much growth from any of these plants. While they won't grow very much, they will provide a source of fresh herbs during the winter.