Wiktionary
n. An electric lamp designed to promote plant growth by emitting an electromagnetic spectrum appropriate for photosynthesis.
Wikipedia
A grow light or plant light is an artificial light source, generally an electric light, designed to stimulate plant growth by emitting an electromagnetic spectrum appropriate for photosynthesis. Grow lights are used in applications where there is either no naturally occurring light, or where supplemental light is required. For example, in the winter months when the available hours of daylight may be insufficient for the desired plant growth, lights are used to extend the time the plants receive light. If plants do not receive enough light, they will grow long and spindly.
Grow lights either attempt to provide a light spectrum similar to that of the sun, or to provide a spectrum that is more tailored to the needs of the plants being cultivated. Outdoor conditions are mimicked with varying colour, temperatures and spectral outputs from the grow light, as well as varying the lumen output (intensity) of the lamps. Depending on the type of plant being cultivated, the stage of cultivation (e.g. the germination/vegetative phase or the flowering/fruiting phase), and the photoperiod required by the plants, specific ranges of spectrum, luminous efficacy and colour temperature are desirable for use with specific plants and time periods.
Russian botanist Andrei Famintsyn was the first to use artificial light for plant growing and research (1868).
Usage examples of "grow light".
The artificial lighting at work might be a problem, but he'd brought along a grow light bulb, just in case.
Indeed, as we went down Old Montague Street, Arnold fell in with us, and he and I kept double vigil on Jack till the sky began to grow light.
Then I'd pork up to about a hundred kilos eating that syntha crap and not getting any exercise and I'd have to have a permit to grow even one flower in my cubicle and a dispensation for the wattage for a grow light and so on and so forth.
The day had begun to grow light before he was able to get back to sleep.
The sky was just beginning to grow light, the sun still hidden behind the mountains.
When it began to grow light outside, everyone gave it up and went back to bed.
Theyd sat up most of the night, sipping tea and talking until it had begun to grow light outside.