For the last two years, I have been trying to learn everything I possibly can about growing plants indoors (in bedrooms or a green house) from October-June. Have almost worn out my "G," "O," "L" and "E" keys, bought books, read hundreds of papers. Following is some things I have learned:

Besides growing media and nutrients, the other two major factors that influence fruit production of tomatoes (and likely their relatives: peppers and eggplants) are GDD (Growing Degree Days) and DLI (Daily Light Integral). You can call it 3DLIG!

Phenolgy refers to plants' response to climate, mostly heat. GDD measures the amount of days that contribute to plants growing and ripening fruit. For instance, it takes 1400-1900 GDD for tomatoes to ripen, based on what type of plant it is (early, mid-season, late; determinate or indeterminate; size of fruit, etc.) DLI is a measure of accumulated light in the PAR range the plant receives in a day. Tomatoes and peppers will "grow" under 10-14 moles (that's the measurement used) minimally. To be productive, they need 20-22 moles per day.

Of course, there are limits - if the temps are above 95 or so, blooms have a hard time developing and fruit setting, so calculations of GDD needs to be capped at 95. More than 30 moles per day will not hasten plant development, so that needs to be taken into account.

The bottom line, not including growing media and nutrients, I think an ideal model of lighting and heating for growing indoors should be able to be formulated.

If you have read this far, this is, from an expression from my younger days, where the rubber meets the road.

The idea is to combine the amount of light and heat needed per day to get ripe fruit in the smallest amount of time. I'll use a 400-watt MH light as my example. It provides 36,000 lumens, so to produce 20 moles per day I need to run it 12 hours per day - anything over that is wasted. I want to start harvesting ripe tomatoes 80 days after being transplanted, they are determinate, medium-size fruit that require 1800 GDD to produce ripe fruit. 1800 divided by 80 tells me I need about 22 GD per day if I want to harvest fruit in my time frame. So I need to maintain at least a 77 degree temp (based on toms liking 55 degrees as the minimum temp) or at least average it.

OK, I'll leave now and go talk to my plants! In the words of Billy Joel: You may be right, I may be crazy. Just stuff I found interesting!

Mike