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Do plants grow better in sunlight or artificial light?

Growing plants indoors with artificial light is certainly possible, and there’s a good chance you’re already doing it. Houseplants like ivy are descended from forest bottom dwellers and shade loving plants. They blossom on exposure to natural sunlight but can typically get enough light from a full day’s exposure to your standard fluorescent lights.

The challenge comes in when you’re trying to grow plants that normally need more than what our average artificial lighting level would provide or attempting to stimulate only certain aspects of plant growth.

Sun-loving plants need high intensity light for a full 12 hours or more. If you’re going to grow these plants under artificial lights, you need artificial lights that truly mimic sunlight. There’s a chance you’d need to use halogen lights to meet the needs of these plants, but now you’re going to have to take care not to burn them because halogen lights are so hot.

If you’re trying to grow sprouts, including sprouts for adding to your sandwich, you’ll want to grow them under red lights. If you want to start your seedlings indoors to get a jump start on the growing season, with the intent to transplant them outside later, you’ll want to grow these under red light.

Plants that are grown entirely under red light tend to be tall and spindly – great for salad sprouts and seedlings that will be outside soon. Red light should be the dominant color spectrum if you’re trying to grow tubers and bulbs. Are you trying to develop fruit like tomatoes and berries? Then you want strong red light exposure.

You’ll need something with more red spectrum than incandescent lights, though incandescent lights already provide a high level of red wavelengths. The problem with incandescent bulbs is that they also generate a lot of heat, so putting a plant close to the bulb to give it the most light risks sun-burning it. If the plant is far enough away not to overheat, then you can use standard incandescent bulbs to help them fruit and bloom.

If you want the plant to grow more heads and stems, you’ll want it under at least some blue light. However, even red lights missing the far red spectrum will result in more compact growth than if the entire red spectrum is present. However, if you want a basic flowering bush perfect to sell for placement on someone’s desk, this may be perfect for you.

If you’re trying to grow leafy greens like radishes, lettuce, water cress and spinach, you want to grow them mostly under red light. The red light spectrum encourages leaf growth.

Flowering plants that haven’t yet bloomed can be kept under red light to delay their blooming. They register the long days under red light as the long hot summer. Once you shift to shorter days and some blue lights, they see it as autumn blooming season as having arrived and erupt into a flowery show. If the plants are already flowering, adding red and far red light will stimulate further flowering.

There are only a few cases where you want to grow plants under predominantly blue light. Blue light limits the growth of extensions like leaves. If the plant has grown flowers or heads, exposing it to mostly blue light will prevent it from bushing out further. If you’re planting seeds, exposure to blue light will result in more female seeds and female plants. Blue light is especially useful in aquaponics systems where you’re trying to raise algae and coral.

Fluorescent light bulbs are already biased toward the blue spectrum. A cool white fluorescent bulb, though, covers the entire spectrum. This is why cool white fluorescent bulbs are a good choice for general lighting for indoor growing plants indoors with artificial light.

Note that when you aren’t try to optimize plant growth in some way like trying to maximize leaf growth or the number of flowers, you don’t have to worry about the red-blue spectrum. Instead, simply find artificial lights like Led grow lights that provide the entire spectrum of light. This means that many readily available artificial lights can be used for houseplants or plants you’ve temporarily brought indoors. Or you could use horticultural growing lights that by design provide the entire spectrum.