Best Light for Growing Plants Indoors

Plants need three things to thrive: soil, water and sunlight. Soil and water are easy to come by, but if you’re planning to grow anything other than houseplants indoors, providing sufficient sunlight presents a challenge. Even if your house or apartment has plenty of windows, you likely won’t get sufficient sunlight to keep your indoor garden happy, especially during winter.

That’s when you bring in the “sun” in the form of artificial lighting. “With the right lighting, you can grow peppers, tomatoes, cucumbers, herbs – a wide range of edible plants,” says Paul Thompson, an indoor-garden expert at All Seasons Gardening and Brewing Supply Co. in Nashville, Tennessee. The lighting you choose depends on the area you need to cover and the light requirements of the plant.

Bulbs and Fixtures

Consider the light source and the type of light it provides:

• T5 fluorescent bulbs (T for “tubular,” 5 meaning they measure 5/8 inch in diameter) are a common choice for growing plants indoors. They can be used in reflectors sized to hold from one to eight bulbs in two- to four-foot reflecting fixtures. To provide light to a few plants on a shelf, you may only need a two-foot fixture with a single bulb; to grow vegetables or herbs indoors you may need a 4- to 8-bulb fixture.
• LED lights last longer and use less electricity than fluorescent bulbs. They are more durable and won’t shatter as easily as glass bulbs. LED bulbs produced especially for plants provide better light than bulbs designed for everyday use.
• HID lights – high-intensity discharge – produce brighter, more intense light that’s better for vegetables or flowers, and covers a larger area. The ballast in the fixture allows you to run a 400, 600 or 1,000-watt light on regular household current; a 1,000-watt light can cover up to an 8 x 8-foot area, Thompson says.
• LEC lighting – light-emitting ceramic – is a newer technology, and more efficient in its use of electricity. A fixture pulling 315 watts can sufficiently light a 4 x 4-foot indoor growing space.

Light that mimics sunlight’s full range of warm and cool colors, from red to blue, is best for growing plants – “Blue is for vegetative growth, the red spectrum is for flowers,” Thompson explains. LEC lights provide the full spectrum; LED and T5 fluorescent lights can either be blue or red or can have a blended spectrum. There are two types of HID lights: metal halide and high- pressure sodium lights. The halide lights are more in the blue spectrum, and the sodium lights tend toward the red end of the spectrum, Thompson says.

How to Use Lights for Plants Indoors

• Supplemental light is usually essential for starting seeds indoors. Seedlings that don’t get enough natural or artificial light grow tall and rangy, with weak stems. To grow strong seedlings, the light should be placed close to the tray, and raised as the plants grow taller.
• Seedlings and mature plants growing indoors need more hours of light than you may expect. As a general rule, provide 14 to 18 hours of artificial light with a few hours of darkness each day. A timer set to turn on and off at specific times makes this lighting task easier.
• Lights can also help gardeners in colder climates winter-over outdoor container plants that wouldn’t otherwise survive frosty temperatures. Geraniums, Boston ferns, begonias and other annuals can thrive indoors under lights, inside the home or snug in a garage or outbuilding where they can be kept from freezing. Here, too, a timer can turn the lights on and off automatically. Plants in potting mix under lights may dry out more quickly, so don’t forget to water those containers that are wintering under lights but out of sight.

Best Lights for Houseplants

Different houseplants have different lighting needs, but in general are adapted to less intense light than plants that normally grow outdoors. For houseplants that thrive in lower light conditions, regular room lighting and natural light through windows may be enough. Compact fluorescent, LED and full-spectrum plant light bulbs designed to fit standard fixtures can provide supplemental light to plants that need more.

Common houseplants that thrive in low-light conditions include:

• Peace lily
• Philodendron
• Pothos
• Chinese evergreen
• Cast-iron plant

These popular houseplants need more light:

• Orchids
• African violets
• Indoor palms
• Christmas cactus; Thanksgiving cactus
• Ficus (Weeping fig)