How to Grow Herbs Indoors Under Lights

Co-authored by Rachel Guffey

Last Updated: December 19, 2022 References

Herbs are plants used for culinary and medicinal purposes. Most herbs grow as annuals and perennials outdoors during the spring and summer months, but many herbs can be grown indoors as well. Traditionally, herbs were placed on sunny windowsills indoors to promote growth. However, sustained herb growth indoors requires long periods of intense light. To accommodate for the lighting requirements of herbs, many indoor gardeners now use grow lights to produce larger, healthier plants yielding year-round harvests of herbs. Use these tips to grow herbs indoors under lights.

Method 1

Method 1 of 3:

Determining What Herbs to Grow

1
Evaluate what herbs will thrive indoors. Not all herbs grow well indoors. Short-lived annuals like coriander, dill, and garden cress do not produce continuous crops and are not well suited for indoor growth.
- Consider the following varieties of herbs that will yield healthy plants indoors: Grolau chives (Allium schoenoprasum), Fernleaf or dwarf dill (Anethum graveolens), English mint (Mentha spicata), Greek oregano (Origanum Vulgare hirtum), Blue Boy rosemary (rosmarinus officinalis), Creeping savory (Satureja repandra), Broadleaf thyme (Plectranthus amboinicus), Spice Globe basil (Ocimum basilicum minimum) and Dwarf Garden sage (Salvia officinalis compacta).
2
Determine what quantity of herbs to grow indoors. How many herbs you grow should be determined by how much you will use them. If you use rosemary springs in roasted chicken every week or make homemade pesto from basil leaves regularly, you will need larger quantities of those herbs. If you only use a scattering of oregano on an occasional pizza, then one plant should suffice.

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3
Bring in existing potted herbs for continued winter growth. Many potted perennial herbs will provide continual harvests throughout the winter when provided with the right growing conditions. Consider bringing in perennial herbs like rosemary, sage and tarragon to grow indoors.
- Avoid transplanting perennials herbs planted directly in the garden. The transplant shock may kill the plants that normally would return the next growing season. Only choose perennial herbs in pots to grow indoors during the winter months.

Method 2

Method 2 of 3:

Evaluating Indoor Lighting Options

1
Understand the lighting needs of your herbs. Each type of herb requires different lighting conditions for successful growth. Determine the lighting needs based on the herbs you will be growing indoors. In general, most herbs require 10 to 16 hours of supplemental light.
- Evaluate the light intensity required for your herbs. The light intensity will be determined by the bulb wattage of the indoor lights and how close the plant needs to be to the light source. The brightness of an indoor light is measured in foot candles or lumens. Foot candles refers to the amount of light hitting a given area, while lumens is the amount of light at the actual light source. Most herbs and vegetable plants require a high light intensity to yield a harvest.
- Evaluate the light spectrum color best suited for your herbs. Natural sunlight contains a complete light spectrum, from red to yellow to violet. While herbs require a full color spectrum for photosynthesis, blue and red light are most critical. Blue light regulates plant growth, while red light stimulates flowering and vegetative growth.
2
Consider fluorescent lighting for your herbs. Fluorescent tubes are a low intensity lighting option ideal for herbs. Fluorescent lighting provides 60 to 80 lumens per watt, which is 2 to 3 times more light than incandescent bulbs. At a distance of 6 inches (15.2 cm) away from the bulbs, fluorescents provide 700 foot (213.4 m) candles; at a distance of 12 inches (30.5 cm) away, they provide 450 foot (137.2 m) candles.
- Choose full-spectrum fluorescent lighting that most closely mimics natural light.^{[1]
  X
  Expert Source
  
  Rachel Guffey
  Plant Specialist
  Expert Interview. 5 August 2021.} The light color is created by a phosphor coating on the inside of the bulb. If full-spectrum natural light tubes are not available, use a combination of standard warm- and cool-white tubes.
- Place herbs close to the fluorescent lighting source, preferably no more than 8 inches (20.3 cm) from the tube, to accommodate for the lower intensity lighting.
- Select fluorescent lighting as the least expensive option for indoor gardening.
3
Consider high-intensity discharge (HID) lights. Most commercial herb producers utilize HID lamps to grow herbs indoors. They typically produce 2 times more light than incandescent or fluorescent bulbs. HID lighting provides 120 to 130 lumens per watt, and is available in 150-watt to 1,000-watt bulbs. At a distance of 3 feet (.9 m) away from the bulbs, 400-watt HID lights provide 1,000 foot (304.8 m) candles and can illuminate about 25 square feet (7.6 square meters).
- Choose metal halide or high-pressure sodium HID lights. Metal halide HID lights give off a bluish-white light that promotes strong plant growth. High-pressure sodium lamps are the most energy efficient HID lighting option, and give off a reddish light.
- Place herbs several feet or meters away from the HID lighting source to ensure the lights don't burn the vegetation.
- Choose HID lights for energy-efficient lighting.

Method 3

Method 3 of 3:

Growing Herbs Indoors

1
Select a location to grow herbs indoors. When using indoor lights, you can grow herbs in almost any location in your home. The most important factor is temperature. Herbs grow best in temperatures below 70 degrees F (21.1 degrees C). Do not locate the herbs near a heat source, such as a heat vent or radiator.
- Consider the humidity. Herbs require ample humidity to promote growth. If the air in your home is dry, place the herb containers in a tray lined with small stones. Fill the tray with enough water to reach the bottom of each container. The water will provide a humid environment ideal for growing herbs.
2
Provide adequate lighting. The intensity of your light source will determine how much light is required for your herbs each day. In general, most herbs need 10 to 16 hours of supplemental light.
- Maintain proper distance between the herbs and the light source.^{[2]
  X
  Expert Source
  
  Rachel Guffey
  Plant Specialist
  Expert Interview. 5 August 2021.} The distance will vary depending on the type of light source you utilize. To determine if the light source is too close, place your hand where the light hits the herb plant. If you feel warmth from the light, it is too close.
- In general, your light should be between 6 and 12 in (15 and 30 cm) away from the plant.^{[3]
  X
  Expert Source
  
  Rachel Guffey
  Plant Specialist
  Expert Interview. 5 August 2021.}
- Rotate the plants each week if you use fluorescent indoor lighting. Fluorescent bulbs are more intense at the center than at the ends, so rotate the plants weekly to ensure even light coverage.
3
Grow herbs in proper soil. Most herbs thrive in soils with pH levels between 6 and 7. To improve drainage, plant herbs in a compost-based soil mixed with sand, peat moss or perlite.
4
Water herbs regularly. After the initial planting, water herbs when the soil feels dry. Water thoroughly until you see water coming out of the bottom of the pot. Do not overwater indoor herbs, or the plants may become waterlogged, yellowish or develop mildew diseases.
5
Fertilize herbs. Most indoor herbs benefit from occasional feeding with an all-purpose water soluble fertilizer, fish emulsion or seaweed. In general, fertilize herbs every 2 weeks and follow the instructions based on the fertilizer type. Only feed plants when they are actively growing and do not over-fertilize. Too much fertilize may kill the herb plants.
6
Cultivate herbs. To promote continued growth and longevity, harvest the herbs regularly. Trim back all plants to prevent flowering. Once the herb flowers, its energy will go toward flower production, rather than plant growth, which will shorten its life.

Community Q&A

Question

I have a 300 watt Mars hydro LED light for my indoor herbs. How long should I leave it on each day?

Community Answer

Fourteen to 18 hours of light a day is normal. Plants can handle 24 hours of light just fine. LED lights are excellent for growing plants indoors.

Warnings

Some herbs can be poisonous to humans and animals. Research the toxicity of the herbs you are growing. Do not grow toxic herbs indoors where small children or pets may access them.

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