HelpfulGardener.com

is there a chart of the hours of light and darkness need of each phase of plant growth?

As a general guide line for my systems I use 16 hours of light for seedlings and veg. stages, then cut back to 12 hours of light for the bloom stage. Some plants don't care, some are extremely picky so it depends on what your growing.

As for a chart, no, I did some searches on google and came up with no actual charts. Maybe some one else can help locate one for you.

hydroguy

What periods are folks using for lettuce? It seems like mine do not do well over 12 hours of light a day.

It was not a controlled experiment though.

Currently have Simpson Elite and Black Seeded Simpson, both leaf lettuces, in a flood tray and they are on 16 hours. Harvest every 5 days. PPM for lettuces run around 400.

hydroguy