Have you been looking to start an indoor garden, but find all the information and options for grow lights a little overwhelming? Read through our article “Lighting 101″ for a breakdown on all the basics.

Introduction

Until about 25 years ago most of the indoor horticulture lighting was done with standard fluorescents. These lights were only applicable for lower light plants like African violets and orchids. Once High Intensity Discharge (HID) lights came on the scene it revolutionized indoor and greenhouse horticulture. With these stronger light systems it was now possible to grow anything anywhere you wanted. Gardeners in apartments, condos and other urban dwellings could have the gardens that used to require an outside plot of land. The advances of horticultural lighting did not stop with HID systems, it continued to develop with high output fluorescents and LEDs. In this article we will review the key points of indoor lighting and the various types of lighting. This info will hopefully help you decide which system is right for you and get you quickly on the way to growing stunning flowers, wholesome vegetables and decorative plants indoors.

Spectrum

Photosynthesis is the action of a plant turning light into energy. The wavelengths of light that a plant can use for photosynthesis are limited. For example most plants cannot accept green light, they reflect it back and that is why they appear green to us. Indoor garden lights are constructed to put out as much usable light as possible by putting out the right spectrum.

Plants use more light from the blue side of the spectrum during vegetative leafy growth. During flowering they use more light from the red side of the spectrum. By changing the spectrum your light emits you can mimic the Sun’s springtime blues or the fall orange/reds anytime of the year.

The specific range of the spectrum that plants utilize is between 400 and 700 nanometers (nm). This area is referred to as the Photosynthetically Active Radiation (PAR) zone. Light spectrum can also be measured by kelvin temperature. Kelvin is used as an expression of the exact color emitted by a bulb. Horticultural bulbs will have a kelvin rating between 2200 and 6500.

Photoperiods

No matter the type of plant it is never a good idea to supply 24 hours of light. Plants need the dark time to go through certain processes that they cannot do during photosynthesis. Plants exude excess water vapor & CO2, as well transport chemicals and enzymes throughout the night. They basically need their rest. 18 hours on and 6 hours off is the best starting schedule for your light system.

For some plants you can induce flowering by shortening the light cycle. This mimics the shorting of the days in nature signaling to the plant that winter is coming and it needs to go to flower and seed. These plants are called Short Day Plants. For these types of plants you will want to change your light cycle to 12 hours on and 12 hours off at the point you want to start flowering.

Day Neutral plants will just flower based off maturity. So keeping the light cycle at 18 hours on and 6 off works just fine. Be sure to research your plant and choose the appropriate photoperiod.

High Intensity Discharge Lights

High intensity Discharge (HID) lights are not just in the horticulture industry. They are the same type of high powered lighting used to illuminate stadiums, streets and parks. However, the industrial HID lights are not manufactured with a garden in mind. They are designed for extended use in outdoor environments not to maximize efficiency and spectrum. Lighting is the number one component in any indoor garden so be sure to invest in the right type of equipment.

HID lights are available in three types: High Pressure Sodium (HPS), Metal Halide (MH) and Mercury Vapor (MV). Only two of these types are used in Horticulture, the HPS and MH. Metal Halides emit blue light used in the early vegetative cycle of a plants development. High Pressure Sodiums emit more orange/red light used during the flowering cycle.

Using a MH early on and switching to a HPS at flowering will give you the best results. Years ago this was difficult as you would have to purchase multiple light systems or pricy conversion bulbs. Today there are the much more cost effective options of switchable ballasts and electronic ballasts. Switchable ballasts have the components to run either type of lamp with the flip of a switch. Electronic ballasts can also run either type but, without the need to manually adjust it.

HID lights are available in 150, 250, 400, 600 & 1000 watts. The wattage of the system is directly related to how much garden area it covers. It is hard to have too much light, but easy to have too much heat and too much electrical cost. Be sure to get the right size for your area.

Tip: If you feel you want to start small and look to expand later on then check out the electronic ballasts. Many have a dimmable feature which can help you reduce the wattage for smaller areas.

T5 Fluorescent Lighting

These aren’t your parents’ fluorescents! T5 High Output Fluorescents are much stronger than traditional fluorescent lighting. Although not as bright as HID lights the T5 produces much less heat and work great for vegging or for taking smaller stature plants full term.

The “T” in T5 refers to the pin style and the “5” refers to the diameter. The standard fluorescent tubes you may be used to are T12 lamps. A T5 lamp is a 5/8-inch diameter lamp, about 40 percent smaller than T12 lamps. The thinner lamps enable better photo-optic control of the light produced by the fixture, increasing efficiency and providing uniform distribution of its light output. The T5 lamps require specialized digital ballast to ignite and won’t work in standard shop lights.

T5 lamps come in two spectrums, 6500 kelvin and 3000 kelvin. The fixtures can run either type of lamp or a combination of the two. The 6500 Kelvin lamps emit blue light and should be used for the vegetative cycle of a plants development. The 3000 Kelvin lamps emit orange/red light and should be mixed in with the 6500 Kelvin (about half and half) if used for the flowering cycle.

T5 fluorescents produce about 95 lumens per watt, compared to 140 lumens per watt from an HPS. Because of the lower light output we recommend T5 for vegging only or for plants that will stay 2 feet or shorter.

Compact Fluorescents are another high output fluorescent, although their lumens per watt ratings are much lower. But if you are in a tight spot that can’t fit a 4 foot or 2 foot T5 light then the compact fluorescent would be a good alternative option.

LEDs

Light Emitting Diode (LED) grow lights are latest fad to hit the indoor growing market. They have made countless improvements to the original models that came out a few years back. However, they still do not compare to the plant producing power of HIDs or T5s. Their big advantages are little to no heat output and very low electrical cost. They are dialed in to the exact spectrum plants need but their lumen output or total brightness is still relatively low.

They work great as supplemental lighting used in conjunction with HID, T5 or natural sunlight. The jury is still out on using LED grow lights as a stand-alone light source. Most of the testing we have done in store has been somewhat lackluster. But if you are looking to experiment on the frontier of the future of lighting LEDs may be the right choice for you.