Those of us who live in the northern part of the US have often been challenged to find a suitable spot indoors to overwinter plants that are not cold-hardy and a place to start vegetables and flowering plants. Many of us can’t grow plants like habaneros that require a long growing season unless we start them indoors in January.
A revolution in plant lighting has taken place over the past few years, with LED grow lights now being marketed to replace high-intensity discharge (HID) lamps and natural light T5 fluorescent tubes. LED grow lights have been touted as the solution for many indoor plant lighting problems. But are they ready for prime time? And are they right for your indoor plants?
HID (HPS and metal halide) lights are bright but bulky and inefficient at using electrical energy, generating lots of heat. That makes them expensive to use and unsuitable for the living areas of a house or apartment.
Cooler and 80% more efficient
So it’s good news that LED grow lights are 80% more efficient than the heat-generating HPS and metal halide lamps. That means LEDs run cool, about room temperature, and they are also effective at promoting plant growth.
Because LED grow-light arrays are available with lamps that output different wavelengths of the light spectrum, they can be made with just the right light for your plants’ needs at various stages in their life cycles. Some arrays include lamps that emit light at three, four or five different wavelengths, and one manufacturer offers an array of 11 wavelengths.
There is a trend toward using higher wattage LED lamps, which produce more light in a compact space. These larger LED lamps, though brighter, may or may not be more efficient than using a larger array or a series of arrays of smaller lamps. Time will tell.
LED arrays are convenient
Arrays are available in various shapes, including spotlights that can be screwed into incandescent or CFL light fixtures such as floor lamps; large and small flat panels of hundreds of LED s that can be hung over your trays; or relatively high-wattage round disks of LEDs that can cover a larger area. This makes them suitable for use in a wide variety of places in your home – for plants on the floor, on a table or on a shelf. There are also large, commercial versions suitable for use in greenhouses. Flat panel arrays can be hung adjacent to one another, and some are made to be electrically daisy-chained.
The lowest effective wattage for home use is around 28 watts for a light-weight panel that will light a 2’x2’ area, suitable for growing seedlings. The array is hung 1 to 2 feet over the tray. Users say it also works fine for larger plants though ideally it would be supplemented with a second array, or with natural or fluorescent light. 90-watt arrays have become popular as their prices have dropped and now cost under $300. LED arrays of 120, 300 and 600 watts are also currently available. The larger ones are hung at 2 feet or higher above the plants and would typically be used in a greenhouse application.
Like other grow lights, LED arrays should be plugged into a timer and switched on for about 12 hours a day for established plants and about 16 hours a day for seedlings.
Sources and prices
Some manufacturers and marketers (prices are subject to change). Also see the retailers’ links at the bottom.
Are they right for you?
While LED grow lights are still more expensive than HID systems, their lower energy use will result in energy cost savings over time. Useful life of LEDs is about 50,000 hours.
So, are LED grow lights right for your indoor plant needs? Perhaps they are. They are certainly more efficient, as well as more expensive, than the rows of fluorescents I used to use to start my veggies.
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