Do Hydroponics Need Sunlight?

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By Emily Cooper

A hydroponics system doesn’t need natural sunlight if you use suitable artificial lighting. Light is one of the most essential factors for plant growth. All plants need light to promote photosynthesis.

Photosynthesis is how plants convert light, water, and oxygen into energy. Without light, plants would not grow, bloom, or produce seeds.

While sunlight is critical for plant growth, you can choose from a wide range of artificial grow lights.

You might also like: Which Hydroponic System Is Best For Vegetables

How Much Light Does a Hydroponic Garden Need?

Plants that are grown hydroponically in soilless growing media often need the same amount of sunlight as plants grown in soil.

Vegetables and plants that flower or bear fruit typically need at least 12 to 16 hours of bright sunlight each day. Four to six hours of the day should include direct sunlight.

Sunlight is necessary for photosynthesis, which is essentially the digestive process used by plants.

First, plants absorb nutrients and water through their roots. Plants also absorb carbon dioxide through the leaves. However, plants need the energy to convert nutrients and water into energy.

When plants receive sunlight, the leaves produce a chemical called chlorophyll. When water, carbon dioxide, and chlorophyll mix with sunlight, the plant produces oxygen and glucose. The oxygen is released into the atmosphere while the plant uses glucose as energy.

Without sunlight, plants cannot produce glucose. Yet, darkness is also an important part of the growth cycle. Plants need darkness to rest and metabolize the nutrients obtained throughout the day.

Do Grow Lights Count as Direct Sunlight?

Grow lights are often used for hydroponic gardening. A grow light typically needs to provide “full-spectrum” light to match the intensity of direct sunlight.

do grow lights count as direct sunlight

The electromagnetic spectrum is divided into seven regions based on the wavelengths produced. The visible light spectrum is the portion of the electromagnetic spectrum that you can see.

The human eye can see wavelengths between 380 and 700 nanometers. Plants primarily respond to the wavelengths between 400 nm and 700nm.

The wavelengths travel through a prism, which separates them into the colors that we see:

  • Violet
  • Indigo
  • Blue
  • Green
  • Yellow
  • Orange
  • Red

Violet and indigo are outside the range of the spectrum needed to promote photosynthesis.

Blue (450 nm) and red (700 nm) are the upper and lower ends of the spectrum for plant growth. Anything outside of these wavelengths contributes to the buildup of heat in the plant’s leaves.

What does this mean for your grow lights?

A grow light that covers the full spectrum provides the most direct alternative to natural light. However, lights that give more of a certain color help with different stages of growth.

For example, lights that cover the blue light spectrum promote better vegetative growth and plant development. Seedlings and young plants benefit most from blue lights.

Explore the main categories of lighting based on the spectrum of wavelengths that they produce.

UV Light Spectrum

The UV light spectrum is not visible to the human eye. UV light produces wavelengths between 100 nm and 400 nm.

Overexposure to UV light can harm plants. However, exposure to small amounts of UV light can be beneficial.

The right amount of UV light may help promote:

  • Increased nutritional value
  • Better taste and aroma
  • Fuller yields
  • Richer colors

These benefits are likely due to the increased growth of specific chemical compounds found in different species of plants.

For example, research suggests that UV-B light may help increase the presence of THC in weed.

Blue Light Spectrum

The blue light spectrum produces electromagnetic wavelengths between 400 nm and 500 nm. Blue light promotes the opening of the pores in the leaves (stomates), which increases CO2 uptake.

The increased CO2 levels enhance the absorption of chlorophyll. With more chlorophyll, plants tend to grow healthier plant root systems and stem structures, which are essential for the future health of the plant.

Green Light Spectrum

The green light spectrum produces wavelengths between 500 nm and 600 nm. Green light is not considered vital to the health of your plants.

Plants absorb most of the green light, but it’s less essential for the absorption of chlorophyll compared to blue lights and red lights.

Red Light Spectrum

Wavelengths between 600 nm and 700 nm produce red light. Red light is the most effective type of light for promoting photosynthesis. It also encourages vegetative growth.

Plants absorb most of the light produced in this spectrum. However, too much red light can lead to stem elongation and plant disfigurement.

Quick Pro Tip: Consider using different types of lights during different stages of growth. Blue spectrum lights are useful during the early stages of growth, as they promote fuller leaves. Red spectrum lights are better for flowering and fruiting.

Choosing the Right Type of Grow Light

The most common types of grow lights include high-intensity discharge (HID) lights, fluorescent lights, and LED grow lights.

Check out our guide for the best hydroponic grow lights

HID lights are powerful and produce a lot of heat and increased light intensity, which may require you to place plants further away. A high-pressure sodium (HPS) light offers more of the red spectrum while metal halide HID lights produce more of the blue spectrum.

Fluorescent lights typically produce a cooler light and may not cover the red spectrum. However, they are affordable and tend to last a long time.

LED grow lights are becoming more popular for setting up a hydroponic lighting system, as they can emit light that covers both the blue and red wavelengths.

Can Hydroponics Work Outside?

A hydroponics garden can be set up outdoors or in a hydroponic greenhouse. An outdoor hydroponic system receives sunlight, which eliminates the need for grow lights.

Growing plants outside also creates extra threats. You may need to worry about severe weather, temperature changes, pests, and damage to your outdoor hydroponic garden.

Drip irrigation systems are among the best choices for outdoor hydroponics. You can easily run the tubing needed for the irrigation system along the ground.

Any electrical components need to be shielded against rain and extreme temperatures. Setting it up inside a greenhouse provides suitable protection and may keep animals away.


Hydroponic plants need light, but you can use natural light or artificial light. Using an LED bulb is the most common option for a household hydroponic system.

LED grow lights can produce specific wavelengths of light, allowing you to recreate the effects of natural light for an indoor garden.

Full-spectrum lights offer the closest alternative to real sunlight for growing plants indoors. However, choosing a different spectrum may promote better yields.

Use blue spectrum lights to encourage fuller growth during the vegetative stage. Switch to a red spectrum light to encourage flowering.