Total-control Indoor Gardening with Modern Hydrop

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Lights

Plant life evolved naturally in the full spectrum of sunlight-from high-frequency ultraviolet, through the visible spectrum, to low-frequency infrared or heat energy. Plants ignore the extremes but use the entire visible spectrum depending more on blue end frequencies early in the season (when the sun is high and near Earth and rapid growth occurs) and on red-end ones in late summer, when the sun is getting lower and flowers and fruit are forming. Not only do plants need the full spectrum of sunlight, but most full-sun-loving food producing plants prefer 14 to 16 hours a day of it, at full dawn-to-dusk natural strength.

Light is measured in lumens (lux) and footcandles (Q. For what good it will do us, a footcandle is the amount of light a 15th century table candle delivers at a 12" distance. Lumens (lux) is the amount of light that same candle throws on a foot square area; approximately ten times the fc. Full summer noontime equatorial sun delivers about 10,000fc, but most plants need only half of this: 6,000fc tops. Any more can burn leaves and dehydrate plant tissues. A minimum of 1,000fc is needed for photosynthesis and survival.

To satisfy most food plants' needs, an artificial lighting system must deliver 2,000fc to 5,000fc to the leaves. A bank of four 40watt fluorescent full-spectrum "Gro-Lites" delivers only about 1,500fc. This is fine for seedlings, African violets, and other low-fight plants. But it's a fraction of what a tomato plant needs—just a bit above base survival. Small wonder that tomato seedlings go leggy and try to climb up into fluorescent lights.

You can buy full-spectrum incandescent GroLite bulbs and mount them in $2 hardware store sockets. A 100-watt floodlamp GroLite will deliver twice the light of a 40-watt fluorescent, but it takes 35 of them to cover a 4' x 4' area with enough energy to satisfy a tomato plant. At about $10 each, the lamps alone would run you $350. Using 3,500 watts of electricity and running them for a 16 hour photoperiod would cost about $3.50. You'd need seventy 40-watt, 48"-long fullspectrum fluorescents to produce the same light ... well, you get the point.

To reproduce the best approximation of true full sunlight, the greenhouse industry has brought us high-intensity-discharge (HID) lamps. A single 500-watt lamp will light the 4'square area (16 square feet) that will grow salads for a family all winter at a cost of less than $.50 in electric charges per 16-hour photoperiod. The lamps are costly at about $75 apiece, only last a few years, require an expensive heavy ballast to pull sufficient amperage to fire them off, and need a heavy screw-in fixture and metal shade that can handle the heat they generate. They will explode if spattered with water, so they need protective safetyglass shields to rate UL approval and should not be used around unsupervised small children.

Expect to pay a minimum of $300 for a single fixture, complete. That seems high, but it's the only practical artificiallight option. Sun energy is free, but a room full of HID lamps is cheaper to buy and operate than the hydroponic greenhouse needed to harness that free energy.

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