Grow lights are used by professionals to produce out of season fruits and vegetables and to head start plantlets in inclement weather. Hobbyists use them to create indoor gardens that can add an unusual design element to any house. Indoor gardens are also used in schools to teach kids.

Getting the light right

Indoor lights are used to substitute sunlight. Not any kind of light will do the job of a good grow light. There is a basic difference in the way we see light and the way plants utilize it. Human beings are not much affected by the color of light but for plants light color is absolutely vital. Plants harness light with the help of pigments the most common of which is chlorophyll. There are others like xanthophylls, carotenoids etc. but chlorophyll is the single most important pigment. Chlorophyll reflects green light – that is why plants appear green. If a plant were to be grown under green light it would not be able to produce any food as it won’t be able to absorb any of the light! Chlorophyll has two light absorption peaks – one in the blue region (700nm wavelength) of the light spectrum and the other in the red region (400 nm wavelength).

Apart from the basic science behind photosynthesis plants generally prefer red light prior to their flowering stage. This is because light receptors in plants are activated by light in the red portion of the spectrum and initiate a complex biochemical pathway that induces flowering in plants.

• Larger plants need more light
• Vegetables typically need more light while Shade plants can make do with small amounts of light.
• Plants need both light and dark periods. The dark periods are particularly important for flowering.
• In an indoor setting, it is the amount of light falling per square foot of surface that is important and not the amount of light emitted per bulb.
• The unit of light appropriate for indoor cultivation of plants is NOT Lux (1 lumen per square foot) but PAR per square foot (PAR = Photosynthetically Active Radiation).
• You can choose to have a full spectrum light source that will deliver all wavelengths of light and mimic sunlight. Alternately you can choose lights that produce only the most productive wavelengths of light (Blue and red). The advantage with the second approach is that electricity consumption and heat generation are far lower.

Grow Light -Options

Incandescent lights, fluorescent lamps, HID lamps (high intensity discharge), HPS (High Pressure Sodium) lamps and LED lights are the different options that are available.
Incandescent bulbs produce warm light but are so inefficient at light production that they have become obsolete for use as indoor horticulture lights.  HID, HPS and fluorescent lights are used but are rapidly being replaced by LED grow lights.

HID and HPS lights produce a lot of heat. A 1000 watt lamp emits only 250 watt worth of light and 750 watts of heat!  LEDs are 4 to 10 times more efficient. They let growers – professional or hobbyists cut electricity costs manifold. An added advantage is that LED grow lights last 50,000 hours or more. So there are no replacement hassles. Indeed it was this that prompted scientists at NASA to use LED lights for growing plants in space!

NASA scientists could either carry a large supply of replacement bulbs and designate one guy solely for replacing lights or opt for LEDs. Obviously they chose the latter. The facts that these lights are small, weigh very little, do not contain mercury and produce precise light are other factors in their favor.

LED Grow Lights

Low electricity costs – A 90 watt LED light based system can easily substitute a 1000 watt HPS system. This is because LEDs are more efficient at producing light, do not have a ballast, produce directional light and it is possible to produce light only from the most productive portions of the light spectrum. Assuming 16 hour operation per day and electricity costs to be$ 0.1 per Kwh the cost of operating an LED based system works out to $ 52 per annum versus $ 628 for an HPS system!

Low replacement costs - Long lifespan ensures that maintenance costs are very low. An LED based light system can last 10 – 17 years as against 12 months for HPS bulbs.

Safety - Low voltage operations, low temperature lighting and resistance to shattering add to the safety coefficient of these lights.

Water conservation - Low temperature lighting means that plants do not need to transpire a lot and help in water conservation. You don’t need to water the plants frequently and in the event of your precious plants being left unattended due to emergencies – they will have a far better chance of survival under low temperature lights.

Better leaf and flower health – These lights are perfect for foliage growth and flowering applications. The low temperature light emitted by these bulbs mean that leaves and flowers are healthier and stay fresh longer.

Small and light weight – These lights are easy to install and maneuver.  Their small size means that they can be installed anywhere you want – in corners, on window sills or any other place you may fancy.

Directional light – Light can be directed to ensure that most of it is available to the plants. Moreover preventing light spillover helps reduce light pollution and maintain cordial relations with neighbors who may not share your passion for indoor gardening.

Given the numerous benefits of energy efficient lights it is no surprise that scores of hobbyists, professional growers and managers of greenhouses in schools and other establishments are turning to these lights. These lights teach us an important lesson about how modern technology can help eliminate hazardous metals, reduce carbon emissions and help manage costs better at the same time.