I love my herbs. I'd grow them just for their beauty and the lift I get from brushing up against the wonderfully scented lavender or rosemary. But I also use them to make salves and soaps, and teas and vinegars. And of course it is nice to have some fresh herbs to toss into salads and pasta dishes. So it is a real disappointment for me to have to give them up over long Chicago winters. But I don't have to give them all up and I am experimenting more each season with what may grow inside, just on or near my windowsill. You may want to try it, too.
As you may know, plants are categorized by their life spans. Annuals last for one season only, no matter how nurturing you are. Biennials produce foliage the first year and flowers the second. Perennials come back year after year. And tender perennials are what we call plants that are perennial in warmer climates.
Basil is an annual. You can bring it in and it will grow well inside but don't expect to put it outside next year. However, you can take cuttings of your plant and start new ones just rooting in water. And they are often sold at grocery stores in winter if you didn't get them inside in time or just want more.
Parsley is a biennial. I have found it grows decently inside but not as vigorously as outside. By early next spring it is pooped out. It is worth it though for the fresh taste, and as an indigestion aid I'm told (hence the sprigs put on plates in restaurants). And a little goes a long way for me.
Rosemary is a tender perennial. It grows outside all year in warmer zones. In fact it is a shrub there. Here it has to come inside to survive, but with our dry heat in winter that's a challenge. Humidity is key to keeping it healthy. I mist mine regularly. And even then I have had mixed results in keeping it alive until spring. So I have started harvesting it heavily throughtout the winter in case I miss my chance later on.
Oregano is a perennial and as such, should have a cold period to survive. This is why I have not tried common sage or English lavender indoors (just a tender lavender that lives outside in France). However, last year, come time to bundle up my pots outdoors, I realized that I had two different oreganos and one was not supposed to be hardy in zone 5. So I brought it in. Well that thing took off like wildfire. I have since read that they are really the same plant with different common names so I kept one inside again. And again, it is putting on new growth from the get-go. So all bets are off now and I plan to try thyme this year.
Just to clarify, I am not using grow lights. I did not have one when I first started doing this and I reserve my tabletop one now for edible and annual seedlings to come. One thing that is important though, besides as much natural light as you can give them in winter, is warmth. Many sills are cold or drafty. Putting the plants on sills near radiators helps but they can fry. And the rosemary will definitely dry out there. So try to place them away from the sill if you can and keep tabs on their watering needs. It may be less in winter but maybe not if it's dry inside or they are near a heat source. Also fertilize them. This year I am using a water-soluble seaweed fertilizer every two weeks.
And don't forget to use and enjoy them. Even if you just have them a few more months, it sure helps get you through a cold, gray winter.