Ut oh, now I have an itch to learn about those things and understand!
@sooby 
-- Photoperiod is day length of light ... got that, I think
-- Daylilies are not impacted much by how long or short they are exposed to daylight (photoperiod), so that is not a primary way that they know what season it is, or when to flower.
-- other plants that
are sensitive to amount of daylight for knowing season and when to flower (like tomatoes?), can be impacted by lights from sources that produce light in the red range of the spectrum. That can include incandescent and high pressure sodium lights. Incandescent examples might include (high intensity?) household lamp lights (old or new compact bulb versions), and high pressure sodium lights may be found, for example, near streets or parking areas and used as flood lights, security lights, and also in plant grow lights.
-- The amount of light that would impact plants that are sensitive to daylight for season/bloom can be as little as 10 foot candles. Very roughly, equivalent to 10 candles burning at the center of a circle that is one foot in radius wide? So those sensitive plants, like tomatoes, can be impacted even with low levels of incandescent or high pressure sodium lights.
-- Photosynthesis that plants need for energy takes more than those 10 foot candles. The full range of light that produces photosynthesis (PAR) is 400 to 700 nanometers, which includes all light visible to the human eye, and that must be stronger than the 10 candles in the one-foot-radius circle to enable photosynthesis to take place.
I am sure I've got some of it wrong, but I love to learn new words, try to sharpen understanding of familiar words, and then see if I can say back what I think I learned.
