Grow Herbs Indoors Under Lights

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.

Steps

Determine What Herbs to Grow

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).
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 1 plant should suffice.
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.

Evaluate Indoor Lighting Options

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.
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 {{safesubst:#invoke:convert|convert}} candles; at a distance of 12 inches (30.5 cm) away, they provide {{safesubst:#invoke:convert|convert}} candles.
- Choose full-spectrum fluorescent lighting that most closely mimics natural light. 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.
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 {{safesubst:#invoke:convert|convert}} 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.