Even though the amount of light inside your greenhouse usually depends on the amount of natural sunlight available, it's helpful to understand a bit about plants' light needs. Plants require certain quantities of light for proper growth. Light is often measured in footcandles . Most vegetable plants need at least 1,000 footcandles, but many houseplants can get by with less. Many of our houseplants originated on shady rainforest floors, so are adapted to low light levels.
Taller plants tend to require more light than small, bushy ones.
In geographic areas with chronic low light or long winters, you can use fluorescent or other plant lights to supplement natural sunlight.