Light is the most important factor in any indoor growing environment. It is also the limiting factor in any indoor growing environment. Lighting technology has vastly improved over what it once was and it is continually evolving with new and better technologies. Without good and plentiful light, a plant will not be able to perform photosynthesis, chiefly the main principle by which a plant converts food into energy. Plants are able to use artificial light, so long as it is of the correct growing spectrum & there is plenty of it.

Light is at the heart of all of this; so correct lighting will result in healthy, happy plants being resistant to infections or colonizing hordes of insectoid pests.

High Intensity Discharge (HID) lights are the main source of light in any serious indoor garden. With the application of an HID light, gardeners are no longer limited by the number of lumens in the growing environment. HID lighting is also the most efficient source of indoor lighting available today. These lamps produce 4-6 times as many lumens/watt compared to any incandescent light of the same wattage and will last much longer. Bulbs range in sized from 100 to 1500 watts.

An HID lamp operates with a properly matched transformer, capacitator and lamp bulb which consists of an inner tube filled with a chemical mixture. Basically you have a metal ballast with a cord that goes to the wall outlet and a cord that goes to the socket powering the bulb. A reflective hood sits around the bulb and reflects light onto plants that would otherwise be lost. Reflectors are painted white inside or else will be plated with a highly reflective aluminum or brilliant chrome, which turns out to be highly stylish in a late 1970's disco sort of way. Some reflectors are built to allow for air cooling which exhausts hot air out from the bulb and out of the room.

The main drawbacks to HID lighting systems is that they put out intense heat, which subsequently causes plants to dry out faster, and the fact that they are incapable of providing the entire natural spectrum. HID lights come as close to natural light as human technology can take us, but natural sunlight is still more full and vibrant. There are two types of HID lamps to be aware of, Metal Halides and High Pressure Sodiums.

It is important to understand that HID light system MUST CORRESPOND with the wattage and type of bulb. A 600 watt HPS system cannot run a 1000 watt HPS bulb. Nor can it run a MH bulb if it is a HPS system. This restriction is easing up with the introduction of conversion bulbs which allow more flexibility. HPS conversion bulbs produce sodium light and are designed for use in MH fixtures. MH conversion bulbs produce halide light and are designed for HPS fixtures.

Recent strides in lighting technology have begun to produce metal halide lamps that will reproduce a more balanced spectrum providing more of the orange/red end. The AgroSun Gold in an exemplary example of this new innovation with an amazing 49% more red light provided.

HPS lights, like their MH counterparts have new bulbs which increase their less intense blue end to their spectrum. With the SunAgro (HPS) or the Hortilux, you can get a 25-30% increase in the blue end of the light spectrum. These lamps will produce more natural compact growth.

Fluorescent lighting is mainly used to sprout seedlings and to initiate rooting in nascent cuttings (clones). Your average fluorescent bulb produces 2300 lumens, which is not enough to grow your typical tomato plant (requiring 41,000-46,000 lumens). There are specialized, full spectrum high output fluorescents which will vegetate plants at an acceptable growth rate, but the growth will still be slower and less full than an HID light.

There are some very important benefits to using fluorescent lighting. They are energy efficient, relatively inexpensive, and can emit a wide spectrum of light suitable for most plant growth. They also have a very low heat output. These lights excel at seed sprouting and growing very young plants.

Sidenote: Many films of the 1990's used the madly flickering flourescent to create a lighting effect suggesting an uneasy, paranoid mood or an indepent feature. Don't do this. Buy good, full spectrum flourescents made especially for growing plants. Plants don't want to feel as if they are in a suspense flick. Plants don't even like movies - play them music instead.

Different types of plants require different amounts of light. Lettuce and herbs will need far less light than peppers or tomatoes which must flower to produce their fruit. Some plants grow in the winter and flower in the summer. Most plants grow during the longer days of spring and early summer, and flower as the days shorten in late summer, fall and early winter. These schedules can be easily simulated in an indoor environment.

Just about all plants need a regular period of light and a regular period of dark. During the light stage they will absorb energy. In the dark period they will build organic molecules from the energy they have absorbed. As you reproduce the cycle of nature, consistency is very, very important. Plants love a dependable pattern and will get stressed if it becomes erratic.

A good timer should be used in order to create regular lighting intervals of Lights On / Lights Off. The periods can be scheduled conveniently, so long as plants receive their light and dark at the same time every day. The general range is 6-12 hours of darkness every day. It is important not to disturb the dark periods with light so be carful about visits during that time which may add unwanted light to the room.

Plant Spacing
Inexperienced growers will often make the mistake of cramming too many plants under insufficient light. Without enough light particles to go around, plants will not have enough energy to grow. Growth under these conditions is far from optimal. Plants are weak and ill looking. The best way to prevent this do is to learn how much light plants are receiving using a light meter. A light meter uses a photo-sensitive cell that creates an electrical current when light particles fall on it and displays it in foot candles. From there you can figure out if plants are getting the optimum amounts of light they need.

Maximizing Light Potential
Flat white walls are the easiest and cheapest way to reflect light back onto plants. A quick coat of paint can make a big difference to your crop.

If you'd like to protect the walls of your room and provide even better light reflection, you might want a roll of Black and White Plastic. Flat black on one side, the opposite side is bright bright white. It's easy to hang and is glossy and doesn't crease easily. It's also easy to wipe down in between crops.

A third and excellent option is Mylar, which is shiny and provides an almost mirror like surface for light to bounce off of. It can be slightly difficult to owrk with and must be pulled tightly so as to provide a flat surface. Otherwise you will find it creates annoying crinkles which will diffuse and defflect light in angles away from plant surfaces.

Conversion Bulbs are designed to allow Metal Halide systems to produce High Pressure Sodium light and High Pressure Sodium systems to produce Metal Halide light. This type of bulb allows you to tailor the light source to the growth stage of the plant (again, using halide blue light for growth and sodium red light for flowering/budding) merely by changing bulbs.

Enhanced Spectrum Bulbs are now available which reproduce a more balanced spectrum. This means there are MH bulbs which produce more red/orange light and HPS bulbs which included more blue light for better growth.

Our favorite enhanced spectrum bulb is the AgroSun Gold which boasts a production of 49% more red light than regular Metal Halides. If you only have on lamp in the garden, this is the bulb to pick. It's more like real sunlight than any other single bulb.

Of the HPS enhanced spectrum bulbms, our personal favorite is the Hortilux™ which produce a higher lumen/watt output as well as a more enhance blue spectral output, without any violet and green reduction in the red spectrum.

If you need to clean the bulb, use a towel lightly dampened with window glass cleaner or rubbing alcohol; wipe all fingerprints, dust and impurities from bulb's glass surface. Let dry thoroughly before installing. After cleaning, always handle the glass through a paper towel. Also, make sure bulb is warmed up to room temperature before installing.

When MH bulbs are turned off they should be left to cool for 20 minutes before re-starting. Turning a Metal Halide bulb on when it is already hot severely shortens the life of the bulb and it can affect the intensity of the light. Metal Halides should be replaced after a year of heavy use.

High Pressure Sodium bulbs can be restarted after only 2 or 3 minutes after being turned off, and they should be replaced every two to three years.

A Note About Lumens
The brightness, or amount of light particles emitted from a bulb, is measured in lumens or foot candles . Lumens are the total number of light particles coming from the bulb itself, and foot candles refers to the amount of light falling on a given area. As you move farther away from a light, the lumens stay the same, but the foot candles decrease. Natural sunlight and artificial light falling on a plant are measured in foot-candles (f.c.) while the light emitted by sources such as the sun and electric bulbs are rated in lumens.

There is controversy over the use of lumens as a measure for plant lighting efficiency. This is because lumens take into account human light sensitivity as opposed to plant sensitivity. Many growers feel that other units such as micromoles or par value (photosynthetically active radiation) might be more accurate and helpful units of measurement when referring to greenhouse crops and the plant lights used to grow them.

Horizontal reflectors fit the bulb horizontally. This orientation bounces light off the top of the reflector and shines in downwards in a rectangular or box like pattern. There are different shapes and sizes of horizontal reflectors available. They are hung from two pieces of chain, one at each end of the reflector. Most horizontal reflectors need to be higher up off the plants when compared to vertical reflectors

There are two main kinds of light movers. There are those that move lights in a circular pattern and those that move them back and forth in a straight line. The circular style is best when the width of your grow area is similar to the length. Light movers are capable of carrying a single lamp, but two or three is even better, as this option will supply the most light and plants can be placed closer together. The Sun Circle is designed to carry one, two or three lights in a 360 degree circle, ideally lighting a 10x10 area. The Light Rail 3.5 is a linear light mover capable of carrying one or two lamps in a back-and-forth pattern. It has a six foot track which may be extended to cover the entire length of your room.

240 volt is also considered to be more 'stable' because it uses half the amounts of amps. The equation goes like this Amps x Volts = Watts. 240 volt requires a double pole breaker and requires a different kind of outlet than standard plugs. Many appliance outlets, such as those for washing machines, refrigerators and air conditioners are already wired for 240.

We've created a Lighting Calculator to help you figure out the correct number of lights for your room. It will tell you the wattage per square foot of various lighting configurations of your choosing. Play with it to decide what sort of lighting arrangement you'll need.

For optimum lumens, you'll need between 20 (minimum) and 60 (maximum) watts per square foot. There may be several different arrangements that will give you the optimum light energy. For example if you needed 2400 watt, you could fill that wil (2) 1000 watt lights and a 400 or with (4) 600 watt lights, etc.

Watts of light = Amount of Kilowatts you are running per hour

Example: 2000 Watts = two 1000 watt lights
2000 Watts X 1000 watts/1 kw = 2 kw per hour of use
So now say you are running your lights for 12 hours a day. You then multiply your kwatts per hour by 12 (hours running in the day)
So in our previous example: 2 kwatts/ hour X 12 hours = 24 kilowatts a day
Multiply by days in a month: 24 Kwatts per day X 30 days = 720 Kw per month
Now you take that and multiply it by the rate charged by the electric company.