Tag Archives: grow lights

Lighting Question

I am growing AutoFlowers using your book.

The seeds soaked 17 hrs then put straight to soil have sprouted in 3 days time.

What lighting is required? I currently have 13watt/60 equiv, 40 watt/150 equiv, and a T5 fixture amounting to 110 florescent watts. Right now I have a 13 watter a couple of inches above each seedling.

I think this is your suggestion? If this is fine what would be the next graduated lighting step?

— Maximum Bob

Hey Maximum Bob,

Glad to know your seeds sprouted well.

How much light you need depends on the size of your grow area. The size of your grow area also dictates how many plants you can grow in one space. Since I don’t know the size of your grow area (square feet and space dimensions), how much reflectivity is in the space, or how many plants you have, it’s hard to be very specific, but I can give some general guidelines.

The 26 watt (100 watt equivalent) CFLs put out the most lumens per watt in the CFL family. The T5s have a VERY good lumens per watt ratio, also. Since you said yours is 110 watts equivalent, I am assuming it has two tube lights in it. Is that correct?

Right now, with the light very close to the seedlings, you can probably get away with your 13w equivalent CFL for another week, as long as you leave it on 24 hours per day.

As the plants get bigger and start to take up more room in the area, you will want more light.

If you are limited to the bulbs you described, I would suggest using BOTH the 40 watt equivalent CFL AND the T5 to light your plants as they get bigger. If you keep them 6 – 12 inches above the plants. You may have to adjust their height daily, depending on how close you keep the lights to the plants.

If you have the money to buy more lighting, we would suggest getting any of the following:

1. Multiple 26w CFLs to hang above your plants.

2. A T5 fixture that holds 6 of the 4 foot 54w bulbs to hang above your plants.

3. A couple of 65w (300-350 equivalent) or 85w (400 equivalent) CFLs to hang above your plants.

It’s good to have lots of reflectivity in your grow area. Fairly close walls that are painted a bright white helps, as does a reflective hood.

Hope this helps.


Dr. Grow