A few caveats should be inserted here.
1. An overdriven fixture does 3 things: uses more electricity for light output, burns the bulb phosphors rapidly, can cause unacceptable electronic 'noise' with some ballasts.
2. The same effect can be achieved in many cases by using more fixtures with more bulbs in a given space.
3. Reflectors can dramatically increase light intensity to plants even with normal fixtures
4. Even overdriven fixtures do not produce enough light for some plant situations. This is why metal halide systems are available.
5. The greatest benefit from an overdriven fixture is when high output bulbs are used. These bulbs are NOT cheap. I typically pay $5 per bulb for good quality high lumen bulbs. You can use cheaper bulbs, but the efficiency loss is very high and bulb failure will be rapid.
Since tomatoes are near and dear to my heart I will include a few details of results using both overdriven and standard fluorescent fixtures.
I have been using shoplight fluorescents to grow tomato plants indoors for about 20 years now. The ultimate in cheap is the typical fixture sold in walmart and other box stores. It has a mini magnetic ballast mounted in each end of the fixture. These fixtures typically cost about $9 and last an average of 2 growing seasons. They are a LOUSY investment and they can NOT be overdriven.
I investigated light fixtures thoroughly about 3 years ago and the cheapest electronic ballast fixture available was from Home Depot. I ordered 24 fixtures at $7 each and assembled them on wooden boards with 3 fixtures per level in my plant starting stand. I did not overdrive these lights, I just used more fixtures to increase the light intensity over my seedlings. The results using these fixtures have been very acceptable. Seedlings grow rapidly and are sturdy and healthy. I do not grow large plants with this setup. When the seedlings are potted up to individual cells, they go to the greenhouse for direct sunlight.
DarJones
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