For plants to thrive inside, the right amount of light is absolutely essential. And while natural light is indeed an option in some cases — if you have a big enough window — grow lights put right above your plants will ensure strong, healthy, and robust growth.
Artificial lighting has come a long way since its early beginnings, moving from incandescent to fluorescent to finally, LED illumination. And as grow lights attempt to resemble the sun’s natural light, grow lights that employ LED technology are typically regarded as the best alternative to outside growing.
Today, LED options are pretty plentiful, but unfortunately, not all of them are made the same way. Take careful consideration when selecting your grow light and rigorously assess quality, intensity, lifetime, heat, cost, and energy efficiency.
This guide on LED grow lights will help you, the hydroponic grower, learn everything there is to know about indoor lighting. Read it, learn from it, and identify the best type of grow light for your plants. Oh, and feel free to check out our Hydroponics Hobby Center while you’re at it!
Table of Contents:
- How plants use light to grow
- LED overview
- Factors to consider
- Best full-spectrum LED lights
- Comparing hydroponic grow lights
How Plants Use Light to Grow
Plants are amazing little things, but the process they use to grow and function is even more remarkable. They take in carbon dioxide and water — which reacts in the presence of sunlight — to produce oxygen. But, as you’re probably aware, there’s a little more to it than that. And let’s be honest, unless you’re right out of elementary school, the details are probably a little hazy at this point.
So, let’s do a quick recap on how plants use light to grow.
Photosynthesis Explained
Plants rely on sunlight for photosynthesis. Utilizing the energy that the sun gives, plants produce their own nourishment during this metabolic process. But, for plants to flower and grow, plants must first transform light energy into carbohydrates (or chemical energy). Thus, in the chloroplast of a plant’s leaves, photosynthesis occurs.
The major steps of the photosynthesis process are as follows:
- Chloroplast pigments in plants absorb particular wavelengths of light.
- High-energy electrons are created using the light energy that was gathered.
- High-energy electrons utilize energy to produce a more reliable energy source.
- Utilizing this reliable energy source, carbon dioxide is converted into carbohydrates and subsequently released as oxygen.
In an attempt to replicate this process, manufacturers of grow lights have utilized this information to create a variety of grow lights that can emit light on a selected spectrum and provide the best, most intense light for plants.
In its present form, a grow light is either made to (1) simulate sunshine or (2) cater to a light spectrum that fits the needs of a particular species of plant. And, as different plant species demand varying amounts/types of light during their various growth seasons/stages, indoor gardeners may need a variety of “grow lights options” to provide their plants with the best light possible at every stage of growth.
How Plants are Affected by Too Much or Too Little Light
Pigment: The green pigment in plants — chlorophyll — is not produced when there is insufficient light, and as a result, plants can change color from pale green to yellow to white.
Leggy: Plant stems become “leggy,” or grow long and slender, giving the impression that they are reaching towards the light source.
Lengthy Intervals: The plant develops lengthy intervals between leaf nodes when it receives little light (leaf nodes are the point where a leaf sticks out from the stem).
Losing Leaves: Without enough light, plants may also lose their leaves, particularly older leaves.
Color: A plant with variegated leaves (white and green leaves) may eventually turn all green.
Flowering: Some flowering plants may not develop flower buds.
Bleaching and/or Burning: Plants exposed to excessive light may have leaves that become bleached and burned.
LED Lights Overview
LED grow lights are, hands down, the most effective type of illumination currently available on the market. Used by commercial growers and home-growers alike, LEDs have experienced numerous advancements over the years and have finally surpassed high-intensity discharge grow lights, often known as HID lights, which were once the mainstay in indoor gardens around the world.
LED lights are highly effective and easily outperform their HPS cousins in terms of yield and energy usage; they consume less electricity, emit little heat energy, and nearly all of the power consumed by LED grow lights is converted into light energy that is specifically targeted toward growth (through the use of sophisticated optics, thermal management engineering, and exact spectrum outputs).
As LEDs only release light in a certain range, plants only receive the amount of light they require. In other words, you won’t have to worry about using light that your plants won’t utilize (aka – there’s no wasted electricity). Additionally, LED lights require very little upkeep—usually only the occasional cleaning. And, as many LEDs are tailored for the full growth cycle, growers can utilize a single LED grow light system from beginning to end. Some LED grow lights are even programmable, allowing the operator to individually target the plant at various stages of its development.
How do LED Grow Lights Work?
LED grow lights provide light using “light-emitting diodes” after being hooked into an outlet. These are tiny electronic parts constructed of two different types of semiconductors. One is positive and is referred to as a hole, while the other is negative and is referred to as an electron. Additionally, LED lights use electroluminescence and a semiconductor to produce light; sometimes, in more advanced lights, tiny reflectors in high-tech LEDs enhance and better focus this light.
When an LED receives the right voltage, an electrical current starts to flow across it, causing the holes and electrons to collide. Recombination, a process that occurs as a result of this collision, releases energy through photons.
Modern LEDs are powerful and can emit visible, ultraviolet, and infrared light. Different light rays have an impact on plant growth and the development of flowers and roots. When exposed to both red and blue grow lights, the majority of plant species complete their usual growth cycle.
Adding additional colors like green, deep blue, and far-red aids in the process and can produce plants of superior quality. However, in rare instances, particular light colors by themselves can result in plants with unfavorable growth traits.
Red vs Blue Light
The color spectrum of light ranges from red to blue; some light bulbs create primarily blue light, some primarily red light, and some produce a combination of blue and red light.
Even though a combination of blue and red light is ideal for plant growth, if you’re only growing leafy greens, you can get by with just blue light (but not recommended).
In order to produce flowers or fruit, plants need larger stems, which are aided by light from the red region of the light spectrum.
For example, in trials with lettuce, researchers have shown that lettuce with less blue light has a milder flavor and a flatter texture, while lettuce with more blue light has a “spicier” flavor and a curlier texture.
To find out what kind of light your lightbulb emits, look at its specifications. Red and blue light are produced in equal measure by light bulbs branded as “white light” or “full spectrum.”
Types of Light
Blue light: When used, blue light prompts the stomata, or tiny holes on the leaves that regulate carbon dioxide uptake and water loss, to open. Although blue light encourages the development of bigger leaves, the plants don’t grow as tall as they might under other light colors.
Red light: Red light can both help to initiate and prolong the blossoming process. Red light by itself also encourages plant development, however, the plants appear stretched and elongated and have smaller leaves, which are frequently seen as unfavorable growth traits.
Far Red Light: A plant will believe it is in the shade if there is too much far-red light present on its own. Far-red light can, however, aid in the blossoming process.
Green light: Despite being one of the least effective colors for photosynthesis, green light is nevertheless helpful to the process. Compared to other colors of light, greenlight can reach the lower leaves of a plant and enter them deeper, aiding in their ability to photosynthesize.
Orange light: Orange light at the red end of the color spectrum can aid in promoting photosynthetic activity in plants. This light tint is typically preferred by a portion of chlorophyll B.
Yellow light: Although yellow light does not function as a necessary component of photosynthesis on its own, some plant pigments can absorb it, which can aid some plants in flowering. Yellow light, on the other hand, tends to make a plant grow lanky with a large internode length, which is the distance between the branches on a plant’s main stem.
UV radiation: UV radiation can help to control plant development. With only UV light, plants grow shorter stems and smaller leaves, but the light also makes leaves thicker and tends to make them more colorful, especially in plants with purplish-colored leaves. But too much UV light might cause the leaves to burn.
Depending on the species or variety, plants may respond to each light treatment in a different way. Depending on the stage a plant is in, such as whether it is in the flowering stage or the vegetative stage, a plant may also require varied lighting.
Full Spectrum LED Lights
Full-spectrum LED lights provide a look that is closer to that of natural light. This is due to the fact that these lights are supplementing diodes that mostly emit white light with specific reds and blues, as well as ultraviolet and infrared. When all of these lights come together, a sun-like glow with a slightly pinkish tint is produced.
Full-spectrum LED lights typically include the following features:
Cooling Mechanisms: Despite the fact that LEDs emit less heat than other types of light, they nevertheless require some form of cooling. In order to increase operating efficiency, cooling systems are used in the majority of LED systems.
Controls: To allow you to control the types of light being used, some full-spectrum LED systems include switches/controls built-in. This enables you to select the appropriate light for each stage while turning on and off various lights.
Full Spectrum LED Vs High-Pressure Sodium (HPS)
LEDs are a straightforward, effective, and energy-efficient alternative to high-pressure sodium (HPS) lighting for grow lights. Due to HPS’s frequent bulb replacement requirements and perceived weight and fragility, HPS lights are becoming more and more expensive in the long run.
Although the heat that HPS lamps generate can be useful in a greenhouse environment, it can also present problems for smaller growth areas or vertical farms. On the other hand, LEDs are more environmentally friendly, lighter, and more compact.
Less radiant heat is released by an LED grow lamp, which benefits the nutrients and moisture needs of plants. In HPS lights, heat is directly emitted onto the plants, raising the leaf surface temperature and sometimes overheating the plant.
Advantages of LED Grow Lights
You don’t need a ballast: LED grow lights can be plugged straight into standard wall sockets without needing a ballast.
LEDs have longer lifespans: LED grow lights have a longer lifespan when compared to alternative lighting options.
LEDs run cooler: If you are an indoor grower, the tendency of LED grows lights to run considerably cooler than traditional lights can be very advantageous.
Control over output: Other lights use full light intensity, but these lights can be muted via a remote control or app, giving you more control over the output and using less energy.
LEDs use fewer watts: LED lights are far more energy efficient than comparable HPS lights, which results in significant power bill savings when adopting LEDs.
Easy positioning: LED grow lights typically come in the shape of all-in-one fixtures, making them simpler to employ in confined locations. As a result, there is low risk of heat damage and these lights may be positioned closer to your plants in a small space, saving you room.
LEDs are safer: Compared to traditional lights, LED grow lights don’t get as hot, making them safer to work around.
More control: LED grow lights may be made to emit particular light wavelengths, giving growers more control and the opportunity to discover the configurations that work best for their particular species. This approach can be successful even at the phenotypic level if you are breeding plants and gathering enough information to make informed selections.
Better for the environment: Since LED grow lights don’t utilize lead, mercury, gas, or filament, they are better for the environment. These lights are more adaptable, robust, long-lasting, and efficient than incandescent lights and do not contain a delicate glass bulb.
Disadvantages of LED Grow Lights
Higher startup costs: The cost of LED grow lights is typically higher. However, because of their lower operating costs, you also save money in the long run.
Low heat production: These lights typically don’t generate much heat. Even though this has numerous benefits, if you’re using LEDs to grow plants in a colder indoor environment, you might need to provide more heat.
No standardization: LED grow lights are currently less standardized than other solutions among manufacturers. Comparing prices may become more difficult as a result. However, the market for LED grow lights has advanced significantly, and design principles are becoming more uniform.
Factors to Consider When Choosing a Hydroponic Grow Light
There are four major “light factors” you need to consider before picking out a light: light intensity, distance, quality, and duration.
1. Light Intensity
The brightness of light is its intensity, and sadly, two separate bulbs may indicate their light output using different metrics, making it difficult to compare the quantity of light generated by the two bulbs. That’s because the light intensity is influenced by the separation between a light source and a plant.
And although there are numerous techniques to measure light, the following are some typical metrics you are likely to encounter:
PPF (photosynthetic photon flux), which is measured in micromoles of light per meter per second, is a metric for how much plant-useful light is released by a bulb each second (umol m-2s-1). PPF (photosynthetic photon flux density), a measurement of PPF when it approaches a surface like a plant leaf, may also be seen. As your plants move away from the light source, PPFD decreases.
A foot-candle is the quantity of light that “a surface that is one square foot” and is “one foot from a light source” that is equivalent to the amount of light that one candle provides. Although it’s not used as commonly, older dictionaries may still contain this metric.
Lumens are not as important when thinking about plant lighting. The critical wavelengths that plants require to thrive are not measured by lumens, which only measure how bright the light is to the human eye.
Instead of measuring the actual intensity of the light, Watts measure the amount of energy required to produce light. Both the wattage and another measurement of light intensity, such as PPF, lumens, or foot candles, should be listed on light bulbs. More efficient light bulbs will provide more light with less watts.
2. Plant Distance from Light
When employing heat-producing bulbs, such as incandescent and high-pressure sodium, it is especially crucial to maintain a proper distance between plants and a light source. However, even with LED lighting, it’s still critical to give your plants some distance.
- 4-6 inches for seedlings (move your light up regularly as they grow)
- 6-12 inches for most hydroponically grown vegetables
- Houseplants with foliage: 12–24 inches
- Houseplants with flowers: 6 to 12 inches
3. Quality of Light
Light’s wavelength or color are considered to be its quality. Red, orange, yellow, green, blue, indigo, and violet light make up the visible light spectrum. All hues of light are produced by sunlight.
The term “photosynthetically active radiation” refers to the region of the light spectrum that is used by plants and is mostly made up of red and blue light.
Grow lights that solely generate light from the red and blue wavelengths of the light spectrum have increased in popularity as lighting technologies have gotten more effective.
Before purchasing a grow light, check the package to determine what kind of light it emits; grow lights typically have labels that say blue, red, or white/balanced light/full spectrum.
Leafy greens, non-flowering home plants, and seeds can all be started using blue or mixed light bulbs.
Red or multicolored light bulbs work well for encouraging the development of buds in blooming plants and for keeping the plants at a manageable length.
However, for the majority of plants at any stage of growth, white or mixed/balanced lighting is ideal.
4. Duration of Light
The amount of hours of light a plant requires per day is known as its photoperiod. For flowering response, plants are divided into one of three photoperiod categories: short day, long day, or day-neutral.
If you’re growing somewhere with less natural light, set a timer to provide additional light. The following total number of light hours should be provided to plants by your timer.
- Plant seedlings: 16 to 18 hours daily
- Hydroponic lettuce, herbs, most vegetables: 12 to 14 hours daily
- Houseplants with foliage: 12–14 hours
- Houseplants in bloom: 14–16 hours
LED Buying Considerations
Full-spectrum LED grow lights are among the best lighting alternatives on the market. The following are the main aspects to take into account when choosing full-spectrum LED grow lights to buy:
Size: Full-spectrum LED grow lights are excellent for smaller spaces because other types of grow lights are heavy and large. Your grow room or tent will have more room for other things as the fixtures are often smaller and don’t need reflectors or ballasts.
Cost: Due to the higher efficiency, these lights are generally more expensive up front but cost less over time. Since an LED has a significantly longer lifespan than, say, a typical HPS bulb, you will eventually save money using one. A full-spectrum LED grow lamp arrangement can be used for many years before it needs to be replaced.
Heat: The temperature of your grow space is an important factor, and grow lights can cause the temperature to rise. This is why a grow room’s ventilation system is so important. Full-spectrum LED grow lights, on the other hand, operate more coolly, so this won’t be as big of a problem. If you’re growing plants in a warmer climate, this is very useful.
Reviews: Reviews are extremely important to look at before purchasing a light. Look for both the number of reviews and the quality of reviews. If both of those factors are high, and the subsequent comments are positive, then it’s probably a decent light.
Best Full Spectrum LED Lights
| Grow Light | Marsh Hydro SP150 Indoor Grow Light | Spider Farmer SF 4000 | VIPARSPECTRA P 2000 Grow Light | VIVOSUN VS 1000 Grow Light | Phlizon FD 6500 Grow Light |
|---|---|---|---|---|---|
| Full Spectrum | Yes | Yes | Yes | Yes | Yes |
| LED Draw (W) | 135 | 450 | 200 | 100 | 650 |
| Flowering Footprint | 2' x 2' | 4' x 4' | 4' x 3' | 3' x 3' | 6' x 6' |
| Weight | 4.23 lbs | 14.33 lbs | 11.33 lbs | 3.22 lbs | 39 lbs |
Comparing Hydroponic Grow Lights
| Grow Light Type | Advantages | Disadvantages |
|---|---|---|
| LED (Light Emitting Diode) | Most energy efficient | Can have a high upfront cost |
| Last a long time | Lights can be a little distracting | |
| spectrum of light is wide | ||
| Very little heat produced | ||
| Array of sizes and styles | ||
| Fluorescent | Somewhat energy efficient | Short lifespan |
| Fairly inexpensive | More energy is used when compared to LEDs | |
| Options for wide spectrum (remember to check label) | ||
| Incandescent | Very inexpensive | Is not energy efficient |
| Short lifespan | ||
| Generates heat | ||
| Plants might try to stretch due to far red light | ||
| High Pressure Sodium (HPS) | Covers a wide area | Very large in size and are usually hung; makes them better for large-scale systems |
| commonly used in commercial setups | Older system/technology | |
| Produces a significant amount of heat | ||
| Some of the light is wasted because it falls outside of the plant-available spectrum |