I have plants growing under two 20-watt fluorescent tubes, but they have not done well. Why not?
Undoubtedly the 20-watt tubes helped to improve poor sun exposure, but the foot-candles of illumination they produce are not enough to stimulate strong growth and bloom. You need four 20-watt tubes or two 40’s to produce enough foot-candles to encourage the best flowering in most plants. Many gardeners use twice as many lights to achieve maximum results.
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