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Can LED Lights Grow Plants? (And How to Get Good Results)

Have you ever asked yourself – Can LED lights grow plants? It’d be a fine thing if they could. Imagine being able to harvest as much as you want without having to get your fingers too dirty or worrying about the elements such as frost-protection, over-wintering plants, or whether your plants are getting enough sunlight.

If it were possible, in theory, you could increase the rate of plant production by running LED lights 24/7 to imitate full cycles of sunlight. But, then again, plants do need to rest.

To answer the question of ‘can LED lights grow plants?’, yes, they can, but it’s determined by the type of lighting. For indoor LED lights that are designed for home living such as your bathroom spotlights, then no, as those don’t cover the full spectrum of light. Plants only need up to two-thirds of full spectrum light found in standard home LED lights for white lighting.

The energy plants need from artificial light is found in narrow spectrum LED lights, otherwise referred to as horticultural LED grow lights. A search on LED grow lights yields thousands of results, all with different types, yet all of them with the same red and blue wavelengths.

Understanding the Light Wavelengths Plants Need from LED Lights

The light spectrum of LED lights is measured in nanometers. Some wavelengths are visible, others aren’t. Those that aren’t are referred to as ultraviolet.

The ranges across the light spectrum include:

Ultraviolet

Ultraviolet light spectrums are invisible to the eye. These are under 400 nanometers.

PAR (photosynthetic Active Radiation)

This is the most crucial element for plant growth. The ranges here are between 400 nanometers and 700 nanometers. This is also the visible spectrum of light covering blue light, red light and green light.

Far-Red

Far-red light can be described as near-infrared. This range is between 750 and 850 nanometers.

The Factors Influencing Plant Growth from LED Lights

Pay attention to this part because the LED grow light market is ultra-competitive and dodgy retailers will promise you their lights only emit the exact light spectrum your plants need. That’s a total fallacy because to be able to grow any type of plant under LED grow lights, you need to use the full spectrum of light including green light that’s supposed to only reflect energy, meaning the plants don’t absorb it. Whether they do or don’t, they still need green light for photosynthesis.

For seed germination, PAR light (400 nm to 700 nm) is necessary. For stem elongation, far-red light is more beneficial as it stimulates sunlight. But, too much far-red light can indicate to a plant that it’s in the shade, causing it to stretch too far, resulting in a leggy plant.

At different stages of plant growth, more specific light profiles can enhance the growth rate.

Coverage Needed for Growing Plants with LED Lights

LED grow lights can only be effective if the bulbs used give enough energy to reach the plant. Horticultural grow lights usually have a PPFD measurement in the product description.

PPFD stands for Photosynthetic Photon Flux Density.

PAR (photosynthetic Active Radiation) describes the lumens an LED light gives off, whereas the PPFD rating describes how much of that PAR light actually reaches the plant.

To be useful in any way, you need to know the measurements of your grow area. Most home growers tend to use LED grow lights in a grow space that’s either 2′ x 2′, 3′ x 3′, 4′ x 4′ or if you have a decent size room, 5′ x 5′ can be dedicated to a LED grow light area for harvesting plants.

You’ll need to use enough LED bulbs to cover your grow area, ensuring each plant gets sufficient light.

Spacing for LED Grow Lights

As with all types of artificial grow lights, having them too close or too far away from your plant with affect the growth yields. Also, having them too close, can also cause leaf burn.

This is less of a problem with LED lights as they are the lowest heat producing light systems to use indoors. High Intensity Lights and fluorescent tube lighting (such as T12s) give off far higher levels of heat.

A good rule of thumb with LED lights is to space them around 12-inches to 18-inches apart.

Different lights have different wattages ranging from 1-watt clamp lamps to as high as 1,000-watt complete LED grow systems.

Naturally, the higher the wattage, the more it will cost to power. As LED lamps could need to be run up to 16-hours a day, they can be cost-effective, but the price per plant growth will be determined by the power consumption.

Avoid the myth that buying LED grow lights with a higher wattage will get you more bang for your buck. Low wattage LEDs can still have a high yield. Never base a buying decision on wattage alone.

The PPFD rating tells you how much of the energy consumption is actually going to reach your plant. That’s where to focus your money. On the amount spent on running costs that’s going to reach your plant. Not the low wall wattage that’s supposed to translate to lower running costs. It’s only lower if it’s used, otherwise, it’s wasted energy.

In terms of the amount of energy converted to light, LED is the most cost-effective, however, there is still a 20% loss. LED lights will convert 80% of energy consumed into light output, whereas it’s the opposite with incandescent bulbs which convert 80% of energy as heat making them near useless for indoor gardeners.

The lifespan of LED lights is far longer than any other grow light system for indoor gardeners.

Growing Indoors with LED Lights

Most types of plants can be successfully grown indoors using LED lights. They can be used for overwintering your plants indoors, but whether you should or not depends on what you’re growing.

Some plant species need to hibernate over winter. If this is the case, some LED lights could be used to stimulate outdoor conditions for fewer hours per day while providing protection indoors from the elements.

It’s also possible to use full spectrum LED lights for growing plants indoors from seed, through their vegetation stage and onto flowering by switching the light frequencies they need at the various stages of growth.

Related Reading:

Growing Plants Indoors with Artificial Lights: All You Need to Know…because LED lights are only one of several options to grow plants indoors cost-effectively. Albeit, a really good one, but there are others including compact fluorescent and high-intensity discharge (HID) lighting.

Can LED Lights Grow Plants? (And How to Get Good Results) was last modified: August 22nd, 2019 by The Practical Planter

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