However, if a grower wanted more light, they’d also get increased amounts of heat. And that could burn their plants. That’s where LEDs can be useful for the growing process. With LEDs, farmers can disconnect the heat from the light. This offers a multitude of advantages including what’s called interlighting – a grower can put the lights right down into the rows of growing plants – and this technique can alter the plants in significant ways. For instance, farmers have found they can raise tastier and sturdier tomatoes by lighting the part of the plant that is shaded by the leaves above.
 

This light placement is part of what’s called a growth recipe. What mix of factors will yield the best crops? What soil – if any – is the best? What temperature is ideal? And, of course, to what range of the light spectrum will the plants best respond?
 

A light spectrum shows how much radiation is emitted at each wavelength. Light also can be described as particles, called photons. Each wavelength of light corresponds to a different energy per photon. Shorter wavelengths correspond to a higher energy per photon. For instance, blue photons have almost twice as much energy as deep red photons. 

The highest energy containing light is at the blue end of the color light spectrum. Blue lights have short wavelengths and therefore contain a lot of energy. At the other end of the spectrum, you’ll find deep red light, which has long wavelengths and contains lower energy. Per joule, different colors of light help plants achieve different goals. Blue light, for example, can keep plants more compact when combined with deep red light. Far-red light, which is light at the extreme red end of the visible spectrum (between red and infra-red), can help plants to flower.
 

Farmers can tune the crops to the wishes of the population they’re growing for or steer the crop for desirable traits – for increasing vitamin C in tomatoes or boosting the crispiness of lettuce, for example. However, growing with LEDs is a relatively new field and that means that no one has it down to an exact science yet. Universities such as Wageningen University in the Netherlands and Colorado State University in the USA are continuing to research which growth recipes yield the best results for various crops.