This depends heavily on the type of plant and can range 60 µmols (micromol) for low light requiring microgreens and 1000 µmols for flowering and fruiting plants.

• 60-120 µmols is best for microgreens
• 200-350 µmols is best for leafy greens and herbs
• 350-650 µmols is best for high light requiring herbs and flowering crops in their vegetative stage
• 650-1000 µmols is best for plants in their flowering stage, or fruiting plants in their flowering or fruiting stage

Receiving too much light can be detrimental too. Too much light can cause plants like lettuce to bolt (this is when they send up their flower stalk and the plant goes to seed) which makes it taste bitter and the leaves tougher. Too much light can also damage or burn plants.

For the scientist in you, a µmol (pronounced “micromol”) is a way to measure the amount of a substance, which in this case would be the number of photons passing through a target area. One µmol of light equals just over 62 quadrillion photons.