Lighting can pose the greatest barrier when trying to grow plants indoors, particularly if you don’t have a window which lets in lots of sun. Plants need more time at the lighting when grown under plant lights, but ascertaining how much depends on individual plant requirements, the lighting intensity and the sort of lighting you provide.
Light Spectrum
The quality of lighting affects how much light a plant needs. Plants primarily need light on the blue and red spectrums, which can be best provided using a full-spectrum fluorescent bulb or bulb labeled as an increase light. Another option is to utilize two fluorescent tubesone warm white and one cool white, to provide a more complete spectrum. Incandescent bulbs only provide light on the red spectrum. They also have a shorter life and produce substantial heat, which can damage heat-sensitive plants.
Lighting Intensity
Light intensity is measured in foot candles. Most houseplants need between 50 and 1,000 foot candles out of either artificial sources or out of sunlight. In case the plant only needs low light or receives some light from a window, regular light from ambient lighting fixtures in the area could possibly be sufficient. Plants that need moderate light require at least 250 foot candles, so they will grow better with a little grow light fixture if they are not near a sunny window. Seedlings, particularly vegetables and other which thrive in full sunlight, need 1,000 foot candles or more of light intensity, so intensive grow light fixtures which contain at least four light tubes are essential for most moderate growth. Light intensity also varies dependent on how near the plants sit to the light. By way of example, plants sitting 6 inches beneath a two-light fixture receive 500 foot candles, while those setting 3 ft from the light source only receive 60.
Seedlings and High-Light Plants
For best growth, put seedlings and high-light beneath a four-tube fixture comprising full-spectrum lighting. Set them around 6 inches beneath the lights so they can receive about 900 foot candles of light intensity. You can use a two-tube fixture, but the light intensity will be less and the plants may not grow as well. Seedlings need about 16 to 18 hours of artificial lighting every day. Ensure they receive even light and the most light intensity by putting reflectors around the lighting fixture, which will reflect all of the light onto the tops and sides of the plants.
Low- and Medium-Light Plants
Most frequent houseplants can grow nicely with 12 to 14 hours of artificial lighting if they are not receiving any sunlight. Medium-light plants need about six hours of daily sunlight, so they benefit from a greater light intensity and do best when place no longer than 1 foot away from the lights. Low-light plants usually grow well in shade or with less than four hours of direct sunlight, so you can place them 2 to 3 feet in the fixture. Although these plants possess differing intensity requirements, the quantity of light time is exactly the same when it’s provided by artificial means. If your plants receive some daylight sun but less than fits their requirements, such as by a nearby window, then provide them with an extra two to six hours of artificial lighting in the evening.
