Let There Be Light

Luminous Lessons Your students' curiosity might lead to controlled investigations of light intensity or duration. For example, they might ask: How many hours of light will produce the fastest growth rate? If you use a classroom windowsill, in which plants receive light primarily from one direction, your class may notice the plants' gradual bending toward the light, a response known as phototropism. Consider rotating the units every couple of days, if practical, and using the phototropic response to fuel investigations.

All green plants require light to drive the process of photosynthesis. The higher the light level, the potentially larger your hydroponic harvest, as long as you're adequately meeting other basic needs. If your plants are getting leggy or not growing, the light source is the first factor to check. Keep a close eye on how your plants are responding to light and adjust exposure accordingly.

Natural Light

The sun radiates the full spectrum of light essential to plant life. A greenhouse is a great natural light source for growing hydroponically. A sunny windowsill will suffice for many non-fruiting vegetables, herbs, and flowers if you place your hydroponic unit 1 or 2 feet away from the glass. In climates with a lot of sunlight, make sure your plants get at least four hours per day of shade.

Artificial Light

Fluorescent lights hung in a GrowLab or other setup will suffice for certain crops if kept on 14 to 16 hours per day. While many houseplants and smaller plants with low light requirements (e.g., seedlings, lettuce, or herbs) will thrive in a hydroponics setup under fluorescent lights, commercial hydroponic gardeners and home gardeners wanting to grow larger fruiting and flowering light-loving crops (e.g., tomatoes) to maturity often use special high-intensity discharge lights with metal halide or high-pressure sodium lamps. These provide bright, efficient light closely approximating sunlight, but are significantly more expensive than fluorescent lights. Don't be discouraged from trying tomatoes, peppers, and other fruiting crops under a fluoresent light setup; students in many growing classrooms have done so successfully!

 

Let There Be No Light

 

 

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