Growing Indoors Under Lights

Advantages

A great range of plants can be grown all year round.
Plants can be returned to the light garden after they have passed their peak.
Light gardens can be set up in sunless basements or even closets as small as 1 m by 1.5 m.
Fluorescent light provides downward as well as slanting rays of light drawing plants upward in straight even growth.
Artificial light can be used as a supplement to natural light or on its own.
Many of the natural variations normally experienced by plants during weather or seasonal changes are eliminated.
When intensity, direction and duration of light are continuously uniform, plant growth can benefit remarkably.
Many plants in their natural surroundings go into dormancy to protect themselves from adverse seasonal variations. This dormancy is virtually eliminated so that growth and sometimes flowering can be continuous processes.

Types of light tubes and bulbs

Incandescent bulbs (normal room lights) produce light high in the red end of the colour spectrum. This produces tall but spindly plant growth.
Fluorescent lights generally produce light closer to the blue end of the spectrum. This light yields short, stocky growth.
Incandescent light can be combined with cool white fluorescent in a ratio of 1 watt of incandescent to each 5 to 20 watts of fluorescent. The major problem with using incandescent light is the heat produced by the bulbs. If your growing area is small the heat buildup might be a detriment to good growing conditions. If, however, you are growing in a cool basement the extra heat might be an advantage.
A combination of cool white and warm white fluorescent tubes is practical for many plants. In addition to burning cooler than incandescent, fluorescent tubes are also somewhat more economical to operate per watt. One cool white tube and one warm white or one of the special growth tubes is very effective when growing African violets or ferns.

Lighting

To yield the maximum light values and best balance of red and blue rays fluorescent tubes should be replaced yearly.
Keep the tubes clean.
Use a light meter to test the light output in footcandles. This should be done when the tubes are new and again at regular intervals. When light efficiency drops below the value required by the type of plants you are growing, the tubes should be replaced.
When figuring out how many lights you need, allow for about 20 watts per square foot minimum.
Light values drop very sharply as distance from the tubes increase.
Many plants such as ferns and other foliage plants will do well with lighting as far away as one metre but most flowering plants need to be quite close to the tubes (15-30cm) for best bloom.
Light values are highest near the centre of the tubes and drop off considerably near the ends.
The minimum number of tubes recommended is two. However, the 1.3 m fixtures are better than two 0.6 m fixtures because of the loss of light value near the ends of the tubes.
To increase light intensity place a larger number of tubes side by side. The area around the tubes and above them should either be painted a light colour or lined with aluminum foil for maximum reflection.
Duration of lighting is important. Plants require 10-18 hours of light. All plants need a resting period (6 hours minimum) for long life. If no resting period is given, plants will bloom or grow themselves to death in a relatively short time.
Lights should be on a timer which is preset to turn on and off at regular times each day. This greatly enhances chances of blooming many plants which need an even photo-period to initiate blooms.
Whatever type of fixture you decide on, try to keep the lights adjustable for height so you can change the types of plants you are growing and also allow for plant growth.

Temperature

Optimum temperature varies from one type of plant to another but usually are about 70 to 75 degrees during the daytime. Most plants are best grown with a night time temperature about 10 degrees lower.

Ventilation

Ventilation and circulation are important to supply fresh air containing the oxygen and carbon dioxide necessary to plant growth and photsynthesis. A small fan will keep the air moving slowly, reducing both cold and hot spots and cutting down chances of disease problems which flourish in warm, stagnant, humid air. For convenience put the fan on a timer.

Humidity

Humidity can be increased by placing a layer of plastic film over the plant stand or benches and covering this with marble chips. The plastic should be one piece and wide enough to cover the sides which can be made from 1 inch by 2 inch lumber. This will allow you to keep the chips moist. The water should not be allowed to touch the bottom of the pots. The water evaporates from the stones and humidifies the air around the plants.

Any grouping of plants increases the humidity because moisture transpired by one plant increases humidity for its neighbour. In basement light set-ups, plastic shower curtains can be closed around the light garden area to avoid making the whole basement damp.

If low humidity becomes a problem (it should normally be 50 to 60% maximum for best results), increase it with a cool vapour humidifier. A normal furnace humidifier does not usually provide sufficient humidity.

If your area is too humid, use a dehumidifier (rarely needed if a fan is used). A reliable thermometer and humidity gauge is a worthwhile investment.