A rough guide is about 20-22 moles/day for veggies. To determine the amount of moles, multiply the foot-candles of light the plant is getting by .00048 to get the moles/hr. Then divide 20 by that.

i.e.: Your lamp produces 50,000 lumens and you have it four feet from the plants. You should be getting about 3,000 foot candles (if my math is correct!). 3,000 x .00048 = 1.44. 20 divided by 1.44 = ~14 hours.

Mike

Thanks Mike... but what about photoperiod? I know some plants will only fruit with a certain amount of light and if you give them too much, they won't fruit.

Sugar snap peas will fruit even if they receive 16 hours of daylight.

Mike

Perfect! Thanks a lot Mike! I'll set it to 16 then. That'll be plenty for the strawberries and tomatoes, as well.

I currently have a snow pea under a 1000W MH for 18 hours a day. I planted the seed maybe a month ago and it is still in a 4x4 pot. About a week ago I noticed flower buds, and two days ago I noticed a three inch pod and another one on the way. So you don't necessarily need a HPS lamp in case you were wondering.

antbeez,

The factor for MH is .00051 as compared to .00048 for HPS. For sunlight, it is .00071.

Mike