|Anyone can grow herbs outdoors in spring and summer, and most do. Fresh basil pairs with mozzarella cheese and fresh tomatoes for incredibly delicious summer salads. Some of our favorites can survive the winter outdoors in pots or very well-drained beds. But even the sturdiest of this group, rosemary, is less tasty in winter and other popular herbs like thyme and sage can be damaged and thus unavailable then. All of summer’s harvest can be preserved in one way or another: dried oregano and frozen parsley are staple for soups and dried bean dishes. There’s just no substitute, however, for fresh herbs and every year more gardeners decide to grow them indoors. Many popular herbs are available as small plants in fall and others can be started from seed directly where they’ll be growing. The place to grow herbs is where light is brightest in your home or office, or anywhere you can provide artificial light.
The most successful set-up for growing herbs indoors is the one that delivers your favorite herbs to your windowsill or tabletop. Its design and materials can vary, but certain principles should always be applied.
• varieties and potting mix
Whenever possible, select smaller-leafed herb varieties such as creeping thyme and globe basil. Unless you employ a hydroponic or other soilless growing system, a well-drained potting mix is essential. Indeed, richly organic mixes with fertilizer and moisture-retaining crystals may stay too wet for indoor herb culture. Opt for another, or amend with finely ground bark or sharp sand to insure good drainage. Reliable performers include:
o Globe Basil (Oncimum basilicum‘Spicy Globe’)
o Garlic Chives (Allium tuberosium)
o Oregano (O. ‘Variegata Thumbles’)
o Curled Parsley (P. crispum)
o Silver Thyme (Thymus hybrid ‘Hi Ho’)
o Tricolor Sage (Salvia officianlis ‘Tricolor’)
• containers and containment
The vision of a neat row of small clay pots with saucers lining the windowsill with aromatic herbs is appealing but may dry out quickly on a sunny winter day. Whether clay or the more moisture-retentive plastic pots suit your watering habits, go for 6”-8” pots to cultivate herbs indoors. Traditional flower pot saucers work well, but may leak or sweat onto wood surfaces. Instead, put the pots and saucers onto a larger tray and elevate it if staining is a concern.
• light and humidity
Locate your indoor herb garden in a sunny window, preferably on the west or south side of the house. If the stems stretch and the distance between leaves increases, the light is inadequate. No new growth and pale leaves also indicate that more light is needed. Should sunlight be too strong, leaves may look bronzed or even crispy brown and no amount of watering will rehydrate them. Move the plants if necessary or provide full spectrum artificial light. Traditional gro-light bulbs and fixtures are widely available or any 2 bulb fluorescent fixture can be adapted for indoor gardening. Use one ‘cool white’ and one ‘daylight’ fluorescent together to achieve the full spectrum. Indoor conditions can dry out plant material but adding humidity is simple. Line the tray or saucers under the herb plants with pebbles and mist them along with the plants daily.
• water and nutrition
Water indoor herb plants from the bottom as a routine matter when the top of the soil feels dry. Overwatering can rot roots and dilutes the flavor of the herbs, as can overuse of fertilizers. Once a month, water the pots from the top and promptly drain the saucers. To encourage new growth, add a balanced soluble fertilizer mixed at half strength to the top watering.
• harvest and storage
When herbs are actively growing, your job is to keep using them since clipping promotes new more tasty leaves. Store what you cannot use right away in the crisper drawer of your refrigerator in a ventilated bag.
When you think about it, you may agree that unlike other houseplants, edible herbs do earn their keep. Every time you clip oregano for spaghetti sauce or chives to top a baked potato, indoor herb plants pay you back big-time for the simple care it takes to grow them.
Parts of this blog appeared in an article for MS Gardener magazine in 2010.