by: Charlene Rennick
Light is not white, but is made up of many colours. When light is refracted, it is bent which exposes the colours inside the ray of light. The beams of red, orange, yellow, green, blue, indigo and violet become a dazzling visible array.
For hydroponic use, light should come from the red and blue beams. This kind of light, called PAR (photosynthetically active radiation), is the next best thing to natural sunlight. Fluorescent lights are adequate for plants that do not need much sunlight, but will not help produce anything other than greenery. To really imitate natural sunlight, a range of bulbs that represent the colours of the spectrum will provide the best hydroponic plant growth.
High Intensity Discharge (HID) lights are the best kind for hydroponic use. They are stronger than regular fluorescent lights and provide the maximum amount of PAR for the amount of wattage. There are two types of HID lights: Metal Halide (MH) is from the white/blue part of the spectrum, and High Pressure Sodium (HPS) is from the orange and yellow part of the spectrum. MH is useful for regular leafy growth and HPS will promote bud growth and flowering. MH/HPS conversion bulbs are available which allow switching back and forth with ease.
Hydroponic light is measured by wattage per square foot. Photosynthesis will occur if the wattage is around 20 watts per square foot for low light plants and as high as 50 watts per square foot for vegetation that needs a higher intensity.
The tips of stems and tops of leaves can become scorched if the hydroponic lights are too close to the plants. If the wattage is low or 250W, the bulb should be 12-14 inches away or 16-24 inches from a 400W bulb and have 24 inches between the plant and a 1000W light.
The colour of paint on the walls and ceiling makes a difference too, with lower gloss white paint making the most of your indoor lights. Mylar is even more reflective if you want to get serious and don’t mind the look.
Hydroponically grown plants need roughly 16-18 hours of light per day for normal growth. Some plants need extra light followed by a period of darkness in order to force blooms to flourish inside. Timers can be purchased to help alleviate the need to remember the lighting cycle and to allow you some freedom from your light switch.
Using HID lights extends the growing season in the fall and allows a head start in the spring, but don’t get too carried away! Extending the light beyond 18 hours a day will wear your plants out and cause an untimely demise.