The Basics of Hydroponic Lighting

Herb garden in an apartment kitchen

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Beginners often take up hydroponics because they want to grow their own food but don’t have access to outdoor space. Although natural sunlight is the ideal lighting source for growing plants, artificial lighting for indoor systems can provide a good substitute within the appropriate color spectrum.

Choosing the best lights for your hydro system can be daunting. There are many options on the market. Depending on your system size and type of plants you are growing; some types may be better or more efficient than others.

Outside, a vegetable garden requires around eight hours of direct sun per day. Artificial lighting for a hydroponic garden should imitate the direct and indirect sunlight requirements. You should plan your system on having at least 14 to 16 hours of artificial light, followed by 10 to 12 hours of darkness every day for annuals. The darkness is just as important as the light—just like animals, plants need time to rest and metabolize.

Perennials require a stricter calculation for the lighting schedule to bring the plants through the vegetative (growth) and flowering (production) stages. The easiest way to maintain a lighting schedule is with an automatic electric timer. They are worth the investment because one small mistake or simply forgetting to turn the lights on or off has the potential to dramatically affect your plants' growth and production rates.

Different Plants, Different Needs

An electronic timer is especially necessary if you are growing a variety of different plants. Although you can follow the general guidelines above and have success, some plants do much better with longer or shorter periods of “daylight.” If you have a mix of these in your garden, you will need to figure out a custom schedule. An electric timer allows you to take care of this hassle-free and change it according to your needs as your garden evolves.

Short-day plants: These require a long period of darkness to photosynthesize and produce flowers. If they are exposed to over 12 hours of light per day, they will not flower. Poinsettias, strawberries, cauliflower, and chrysanthemums are short-day plants. The short-day cycle mimics nature's environment for plants the flower in the spring.

Long-day plants: These require up to 18 hours of sunlight per day. They include wheat, lettuce, potatoes, spinach, and turnips. The long-day cycle mimics the natural environment of summer-flowering plants.

Day-neutral plants: These are the most flexible. They produce fruit no matter the level of light exposure. Examples include rice, eggplant, roses, and corn.

If you decide to mix short and long-day plants in one growing system, it is best to compromise their needs and pick a lighting schedule that is right in the middle, around fourteen hours of light per day.

Lighting System Components

All hydro lighting systems have four main parts. These are the bulb, reflector hood, remote ballast, and timer.

Bulb

The most common types of bulbs are LED, fluorescent, metal halide, and high pressure sodium.

  • LEDs (light-emitting diodes) are one of the newest forms of hydroponic lighting. They are the most cost-efficient and energy-efficient methods of lighting. LED grow lights are often sold as either square panels or tubes similar to fluorescents.
  • Fluorescent bulbs work well for starting seeds and the beginning stages of seedlings. The low heat output allows seeds to grow without getting burned or dried out, they also work well for growing salad greens and flowers. 
  • Metal halide bulbs offer strong all-around light. They are good for long-day plants that require more light. MH bulbs help plants that have just finished sprouting and are now entering the growing or vegging stage. 
  • High-Pressure Sodium bulbs are the best choice for the flowering or fruiting stage of your plants. They are more expensive, so are often used in combination with an MH bulb (used during vegetative state) to save money on replacement costs. Although they are more expensive initially, HPS bulbs last up to twice as long as MH, up to five years. But, like MH lights they do lose effectiveness with use and may need to be replaced as often as every two years based on how much use they get.

Reflector hood

The reflector hood is a reflective casing around the bulb. It increases the effectiveness and efficiency of the bulb by reflecting the light down onto the plants at multiple angles, giving a more effective spread. This also allows you to use lights that give off less heat, saving on electricity and cooling costs.

Remote ballast

The ballast is the power box that powers the light. Sometimes ballasts are sold as a part of the lamp assembly, but these are usually far too hot and heavy. Remote ballasts are much better for home systems. This is the most expensive element of the lighting system, so it must be kept off the ground to ensure that it never gets wet in case of a flood or leak. It is recommended to buy the ballast as a set with the bulb because they must match each other in wattage.

Timer

Timers are the least expensive piece of the lighting system, but they are incredibly important. They must be heavy-duty and grounded (three-prong plug) but can be either manual or electric. Manual timers use pins and have two plugs on either side so that you can attach two grow lights at once.

Article Sources
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  1. Preparing a Vegetable Garden Site. University of New Hampshire Extension

  2. Optimizing Plant Growth With Indoor Lighting. University of New Hampshire Extension