Yard and Garden: growing herbs indoors

Aaron J. Steil
Iowa State University Extension and Outreach
Herbs being grown indoors.

AMES, Iowa — Even while the weather is cold outside, it is still possible to enjoy fresh herbs for cooking. Taking advantage of a sunny window in your home can allow for herbs to thrive all year. In this article, Iowa State University Extension and Outreach horticulturists answer questions on how to grow herbs indoors. 

Which herbs are best for growing indoors?

Just about any herb has the potential to be grown indoors. There are, however, a few species that do better with indoor growing conditions. These herbs tolerate the lower light levels, low humidity, and cooler temperatures indoors, making them the best herbs to start with when growing herbs inside your home. Parsley, mint, chives, basil, oregano, cilantro and thyme are all great candidates to grow indoors. While still relatively easy to grow inside, rosemary, sage, lemon balm, marjoram, chervil and bay laurel are good species to try next. 

What growing conditions are best for indoor herbs?

Light is typically the most limiting factor to successfully growing herbs indoors. Plants will need as much direct sunlight as you can provide. Most herbs need around eight hours of direct light each day when grown indoors. A south-facing sunny window is a great candidate, but a bright east or west-facing window can be good as well. 

The typical temperatures found indoors are ideal for herbs. Allow the soil to dry between each watering as most herbs do not tolerate wet soils. Containers should be appropriately sized. Those that are too large stay wet too long. Containers should have good drainage with well-drained potting mix. Clay or terracotta pots are great options for herbs because they are porous and dry out more readily. Grow each species of herb in its own container, as it is difficult to create the best growing conditions for multiple species of herbs in a single container. 

Herbs do not require as much fertilizer as other container plants but they do benefit from periodic light fertilization with a balanced all-purpose fertilizer solution at half or quarter strength. Fertilize in early spring through summer and avoid fertilization during the winter months. 

How can I provide more light for my herbs?

Providing enough light for herbs to grow well indoors, especially during the winter months when days are shorter, is difficult. Some herbs will tolerate as little as six hours of direct light a day but most want eight or more hours each day. When light levels are not adequate, herbs grow well under supplemental light. 

Small grow-light setups are available from many online retailers and garden centers. Gardeners can also build their own grow-light setup. These can range from a compact florescent bulb in a task light fixture for a few plants, to a plug-in 4-foot LED shop light for larger herb collections. Look for full-spectrum grow lights in high-output fixtures. Place lights within 6 to 12 inches of the leaves for higher light intensities. Plug the light into a timer set to be on for 12 to 16 hours a day for ideal growth. 

How do I harvest and use herbs grown indoors?

Harvest herbs indoors as you would if grown outdoors. Most do well with periodic snipping as they are needed in the kitchen. Leafy annual herbs, like basil, chervil, and parsley, can be cut back severely when harvested. Using a sharp knife or pruning shears, cut just above a leaf or pair of leaves. Leave approximately 4 to 6 inches of the stem for later growth. Do not cut back leafy perennial herbs as heavily as annual herbs. On perennials, such as chives, mint, oregano, and thyme, remove the top one-third of growth. 

After several harvests, it is best to discard old annual herbs and start new plants from seed. Once the danger of frost has passed in the spring, perennial and tender perennial herbs, like rosemary, bay laurel and marjoram, can be moved outdoors where the harvest can continue all summer. 

Will indoor grown herbs taste the same as those grown outdoors?

Many indoor grown herbs are not as strong or as intensely flavored compared to those grown outside. However, basil will always taste like basil whether it is grown indoors or outdoors.