This is the second article in our four-part series about indoor plant lighting. You can also read the first, third, and fourth articles.

Typically, insufficient lighting is the limiting factor for indoor plant growth and flowering, plus the reason for spindly seedlings. Most light fixtures in our homes and offices – especially those still using incandescent bulbs or those with energy-saving bulbs that mimic incandescents – don’t give off enough energy for plants to survive or thrive on long-term. In addition, windows block a surprising amount of sunlight intensity compared with the same spot just outside the glass. Insect screening outside a window reduces intensity even more.

Artificial lighting can either supplement natural light or be the sole light source for plants. Plants tolerate levels of light outside of their preferred range, but sensitivities vary from species to species. Over time, the consequences of inappropriate light levels may impact a plant’s health and alter its appearance, even if it isn’t immediately noticeable.

The importance of light to plants

For plants, light is food. We think of fertilizer as plant “food,” but in reality, it is more akin to a multivitamin than it is a meal – it supports how they use their food (carbohydrates from photosynthesis) and helps build tissues, pigments, hormones, defensive chemicals, and so forth – but it’s not providing the calories they need to survive and grow. They certainly can “fast,” so to speak, such as spending a few days in a box in transit or remaining semi-dormant in winter, but prolonged light deprivation from insufficient lighting will have negative impacts on plant health akin to slow starvation.

Plants may lack eyes, but they can still “see” light by detecting its colors, intensity, and duration. Coupled with temperature or precipitation, it can tell them what season it is for the purposes of growth and reproduction (flowering). Weather can fluctuate from year to year, but the patterns of daylength and general light intensity remain the same and are the most reliable environmental cues for the plant.

This is the first article in a four-part series about the ins and outs of gardening under lights, both for newcomers curious about a different way to grow plants and for more experienced growers who want to build on their understanding of lighting options. Read on for the second, third, and fourth parts of the series.

Why use lights for plants?

It’s sensible to think, “why provide artificial light for indoor plants? Isn’t natural window light enough?” After all, natural light is certainly what the plants get when growing outside. If you’re fortunate and have sun-soaked windows in your home, you may have little need for artificial lighting. Anyone who has insufficient window light or who otherwise can’t utilize their windows for growing plants, though, would benefit from giving their plants brighter conditions.

We’ll address this in more detail in upcoming posts, but light levels play a significant role in keeping plants healthy, vigorous, and looking their best. Plant lights give you more control over this aspect of plant care.

Who benefits from using plant lights?

Anyone who doesn’t have ideal natural-light conditions for their plants would benefit from using plant lights (also called “grow lights”). You don’t have to be a tropical plant aficionado to make use of them, and anyone with an available power outlet can try it. Setups can be as simple or as complex as you’d like. Seed-starting enthusiasts can produce more robust seedlings, and anyone trying to overwinter a lemon tree, some herbs, an aloe, or patio tropicals could have more vigorous plants if their winter slog could be brightened with some extra light.