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Is it a good idea to use greenhouse grow lights? Here’s what to know

Pros and cons to greenhouse grow lights

LED lights above plants
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One of the major components of growing any type of plant is light. However, giving your plants the proper amount of light can be a problem. This is where grow lights become a necessity — they can give plants the correct amount of light anywhere in a home or apartment (or even a creepy basement). With that being said, grow lights can be confusing for anyone not familiar with the terminology and the different types available.

On top of that, grow lights have both positives and negatives when used in a greenhouse. When it comes to lighting in a greenhouse, natural light is the best, but greenhouses used in the winter may not be getting enough light, and your plants may need supplemental light — this is where greenhouse grow lights come in. Read on to learn about the basics of greenhouse grow lights.

grow light system
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What are grow lights?

Let’s go back to 10th-grade biology class. Plants need light in order to photosynthesize; specifically, they absorb different parts of the light spectrum than what is visible to humans. Plants primarily use red and blue wavelengths of the spectrum.

For grow lights, there are two major types of bulbs: incandescent and fluorescent. Right away, incandescent bulbs should not be used. They emit red wavelengths but not enough blue, and they produce far too much heat, which can harm most plants. Not only that, but they are also one-third less efficient than fluorescents, making you lose money in the long run.

While regular fluorescents are the way to go, many are not strong enough for plant growth. Instead, go for fluorescent bulbs that are specifically made for growing plants that emit higher amounts of the red wavelength to compensate for the overly blue output of cool white fluorescents.

Grow lights in greenhouse
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Different types of grow lights

Now that you know what grow lights are, it’s time to learn about the different types. Gardeners have different needs, which depend on factors such as their types of plants, the size of their greenhouse, and the amount of light getting into their greenhouse. Grow lights can also be used in combination with each other, so you do not need to choose only one. There are many types of lights, but here are three of the major ones:

  • T-5 bulbs: These are full-spectrum fluorescent lights that can give off a high output. These use far less power than traditional incandescent bulbs and can be used for up to 50,000 hours.
  • High-intensity discharge bulbs (HID): These are best used across a wide area, but be careful. HIDs need to be installed a good distance away from the plants, as these bulbs can run hot. There are two types of HID bulbs. First, high-pressure sodium lights are glowing red lights that are best used for when plants are flowering and/or budding. Second, the halide is a bluish light that stimulates the plant’s growth.
  • Light-emitting diode (LED): The most recent entry in the bulb battle, LEDs are the most popular choice for grow lights because they usually do better in all major categories — think performance, energy efficiency, and lifespan. LED plant lights come in both blue and red lights, are lightweight, and consume 30 percent less energy than fluorescent lights.
Purple grow lights over plants
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Will grow lights work in a greenhouse?

Serious and quick-to-learn amateur plant growers may have invested in a greenhouse and are wondering if grow lights can be used in them. The good news is that grow lights can become a major asset to any greenhouse. The bad news is that some planning is required to avoid disaster. There are four things to keep in mind when buying grow lights for a greenhouse.

1. Grow lights can supplement light

A problem with greenhouses is that they can sometimes not get enough light, especially during the winter. When plants do not get enough light, they tend to grow higher, reaching for more light. They can also become top heavy, and energy that usually goes to leaves and flowers instead transfers to the stem to keep it from falling, weakening the plant. Grow lights can prevent this by providing enough light.

2. They can also provide too much light

During the day, plants absorb light and water to create starch and oxygen. Then, during the night, the plant converts the starch to sugar and stores it. One of the problems with grow lights in a greenhouse is that they can be left on too long, compromising the health of your plants. Too much light can make plants pale, even sunburned. To avoid this, turn off all grow lights at night so that your plants get roughly eight hours of darkness for health maintenance.

3. You need to properly distribute grow lights

A common problem with grow lights in greenhouses is that people tend to distribute them unevenly. This makes some plants grow well as others lag behind. While different plants can have different light requirements, grow lights should generally provide 20 to 40 watts of light per square foot. The light should also reach all leaves on every plant. Make sure not to space the plants too closely, or the leaves will block the light from other plants.

4. Look for waterproof grow lights

A greenhouse can become very humid, the weather can be unpredictable, and watering your plants can leave behind droplets on your supplies. That’s why you want to look for grow lights that are waterproof to ensure that they are safe and long-lasting. If you’re putting in the effort to set up grow lights in your greenhouse, you want to make sure that they work and don’t become damaged in wet conditions. You want your grow lights to be at least water resistant, if not waterproof. An IP65 or IP54 rating is usually sufficient for hobby growers, but a higher rating may be preferable for extra insurance.

When it comes down to it, grow lights are not that hard to understand. That said, do plan out your space before implementing grow lights into a greenhouse. Different types need to be chosen based on your plant variety, the size of the greenhouse, and your available space. While there are a few negatives to using grow lights in a greenhouse, anyone can use them to improve their lighting situation and make their plants grow efficiently.

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Niko Vercelletto lives in Lansing, Michigan. He is passionate about going into depressive spirals thanks to the Detroit Lions…
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