By Kathy Widenhouse, award-winning writer and owner of Tomato Dirt, a leading online source of for growing tomatoes in the home garden.
LED grow lights are used for growing seedlings and plants indoors. The “LED” acronym is short for Light Emitting Diode. In layman’s terms, that means an LED is a device that converts electricity directly into light.
LEDs are becoming a preferred grow light among home gardeners because they are so efficient. If you would like to start seeds indoors or even grow indoor tomatoes, you may want to consider using LED grow lights. (Here are other grow light options to consider, too.)
But first, here’s the dirt about what plants need from grow lights. This information can help you understand why LED grow lights are a good choice for growing tomato seedlings and plants indoors.
Indoor plants grow best with light that is as similar as possible to natural sunlight. As you may remember from your school days, light is made up of waves.
Light waves are tinted on a spectrum ranging from red/orange/yellow waves (defined as “warm tint”) to blue/violet waves (“cool tint”). Each type of light—warm or cool—encourages specific plant behavior. Light waves are measured in numerical values on the Kelvin color temperature scale, like this:
It’s no secret that along with light, plants need water, food, and air circulation to grow their best. As for light, plants need a full spectrum of 2,700 to 6,500 degrees Kelvin to grow their healthiest.
The first LED grow lights emitted a narrow spectrum of light. Some LEDs offered light on the warm end of the continuum, others in the blue range. Gardeners needed blue LEDs to get seedlings started, because blue light waves promote root and leaf growth. Once the seedlings got large enough, gardeners switched to red LED grow lights to provide what the plants needed in order to mature. Red light helps plants to flower and produce fruit.
But now, with technological advances, full spectrum LED lights are available for the home gardener. There’s no need to change out LED grow lights (although some gardeners still prefer to do so.) Today’s LED grow lights offer the full range of color temperature wavelengths that are closest to natural light.
Yes. Standard LED lights offer a limited spectrum of wavelengths, which is fine for the lights in your bedroom or living room. But LED grow lights are different. They have a wider spectrum of both blue (cool) and red (warm) light to promote both vegetative growth and flowering/fruiting. When you choose LED lights for indoor growing, make sure you select those that are purposely manufactured for plants.
You can use any type of LED light to grow indoor plants, but only LED grow lights are most effective because they offer a full spectrum of color.
The impact of light wave color on plant growth
Gardeners have plenty of grow light options. But when compared with fluorescent and HID grow lights, LED grow lights have some distinct advantages.
Like any artificial light system, LED grow lights have a few drawbacks.
Look for “full spectrum” LED grow lights. The most typical color temperature is about 6,500 Kelvin, which is the usual color temperature in natural daylight.
As for size, choose a bulb that fits your grow light system. The most common are T5 and T8 bulbs, in which the "T" refers to a tubular shape. The number indicates the bulb’s diameter in eighths of an inch, making a T5 bulb 5/8 of an inch in diameter and a T8 bulb 8/8 – a full inch in diameter.
Nothing beats natural outdoor light for outdoor crops. But if you want to start tomato seeds indoors or even grow an offseason crop inside, then LEDs are an excellent choice.
LED grow lights are efficient. They offer a full spectrum of light color wavelengths, which imitates natural daylight. And they are available as tubes for trays or as bulbs for specific plants. It’s no wonder that so many home gardeners are choosing LED grow lights for their indoor growing systems.
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