different lights

21 years ago

I have used flouresent lights for start and that works great, when the plants (tomato) start to get bigger, is there any advantage to using metal halide or sodium above the flouresent. My thinking is keep the flouresent right above the plants and add the other light higher up. To give it a more balance light. The other lights I think are too hot to get within 2" of the seedlings. has anyone tried this or is it just not nessacary because the flouresents do a good enough job. thanks.

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Comments (4)

kdjoergensen
21 years ago
If you are going to put MH or Sodium lights up, then move the fluorescents. YOu do not need them. Keep the MH bulbs 2-3 feet above the plants (depending on the watts you are running). Closer than that is not necerssary. Fluorescents need to be just above the canopy. MH/Sodium gives better allround light than fluorescents which focuses of the upper leaves. Bushy plants do better under MH/Sodium.
shrubs_n_bulbs
21 years ago
Metal halide (MH) and high pressure sodium (HPS) lamps are a little more efficient than fluorescents and are easily available in high-wattage fixtures. HPS especially are efficient but produce almost no light in the blue part of the spectrum, so they are rarely used as the sole light source. They are especially prized by marijuana growers to encourage flowering :)

So, if you intend to add a lot more watts with the MH/HPS system, then you can put it further away from the plant and grow a much taller bushier plant. Having done this, the fluorescents are probably redundant and might just be blocking light. You might use them to add some blue light to an HPS lamp.

If you just intend to add, say, 100W of MH to 100W of fluorescent then I'd say don't bother. Its a lot of hassle that gets little more than adding another 100W of fluorescents. The spectrum isn't any better than using the right fluorescent bulb. Use the MH/HPS lamps for what they are good at, which is getting a lot of light from a compact unit. You can also get very high power up to 1000W or so from a single compact fluorescent bulb, but they are a bit less efficient than a MH or HPS lamp.
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caosesvida
Original Author
21 years ago
ok thanks, what I have is a box about 4 foot long and about 12 inches wide and 12 inches deep. What size mh or sodium would you reccomend, I am starting mostly tomato. but it seems that I have ordered more than I bargined for. so my box may not be big enough. so any help here would be appreciated this is the weekend that I put it all together.
johnva
21 years ago
Personally I would use 1 shop light with 2 40w floros in it if it were me. If you plan to grow them to fruit add a second shop light. Otherwise ur energy cost is going to eat u up :)

John