Three Key Questions to Consider Before Choosing Grow Lights

With general lighting, the terms watts and lumens help us to understand how much energy our lights will use (watts) and how much light they will produce (lumens). While these measurements are useful for grow lights, they aren’t the most relevant. Home growers, greenhouse farmers, medicinal plant growers and commercial plant growers all strive to optimize and accelerate plant growth by replicating the ideal conditions for photosynthesis. So, what factors should be considered when purchasing grow lights?

1. What PPF or PPFD measurements are best for the grow lights?

Let’s start back at the basics. The visible light spectrum is a segment of the electromagnetic spectrum (typically between 380 and 750 nanometers) that is visible with the human eye. Plants use a similar section of the spectrum (generally between 400 and 700 nanometers) for photosynthesis. This range of plant-usable light is called Photosynthetically Active Radiation (PAR). PPF and PPFD measurements give information about how much PAR is given off by a light source and how much of that light plants will receive.

PPF (Photosynthetic Photon Flux)measures the amount of plant-usable light given off by a light source. Specifically, the number of micromoles of photons released from a light source per second (µMol/s).

PPFD (Photosynthetic Photon Flux Density)measures the amount of plant-usable light the plants will receive. Specifically, the number of micromoles of photons that land on a square meter per second (µMol/s/m2).

The following are some examples of ranges that may work well for cannabis growth:

Seedling and Clone Stages: 100-300 µMol/s/m2
Vegetation Stage: 400-600 µMol/s/m2
Flowering and Fruit Stages: 800-1000 µMol/s/m2

Recommended PPF and PPFD measurements will vary based on the type of plants, stages of the plants and growth goals for the plants. In the chart below you can see an example of the PPFD of a fixture and how it differs based on the distance of the plant from the light source.

In addition to PPF and PPFD measurements, another important factor to consider is color spectrum.

Grow Lights

2. What color spectrum is best for grow lights?

While the entire electromagnetic spectrum can provide value to plants, the PAR range (400-700nm) is necessary to facilitate photosynthesis. Within this, the color ranges are not valuable in equal amounts though. In a very basic sense, red and blue are the most effective wavelengths for photosynthesis and are highly absorbed. Green and yellow light play a much smaller role in the plant’s development and much of the light is reflected, which is why plants look green.

The goal of a highly effective and efficient greenhouse would be to use the correct balance of light to yield maximum results. This is generally achieved with red, blue or full spectrum lights.

Grow Lights

The term full spectrum has a few meanings. People often think of full spectrum lights as bright white lights that mimic sunlight, but full spectrum can also mean a light that delivers all wavelengths of the electromagnetic spectrum. Bright white lights can be good for growing, but they also generally deliver more green and yellow light than needed. If plants receive more light than they can absorb, energy will be wasted and the light will be reflected as heat, which can be detrimental to plant growth.Many manufacturers offer full spectrum lights targeted to the needs of plants that provide larger amounts of red and blue light and less green and yellow light.

Different wavelengths can also produce unique benefits based on the plant’s stage.

Grow Lights

Blue Spectrum (400-500nm), Ideal for Vegetation Stage

Promotes stomata opening which creates efficient photosynthesis by allowing the exchange of carbon dioxide and oxygen
Allows for peak absorption of chlorophyll
Encourages strong roots and sprouting
Keeps intermodal spacing short and compact

Red Spectrum (600-700nm), Far Red Spectrum (700-800nm), Ideal for Budding, Flowering and Fruit Stages

Enhances photosynthesis to promote growth
Allows for peak absorption of chlorophyll
Alters the state of phytochrome, which modulates the expression of genes and is responsible for growth
Promotes extension and elongation by initiating the shade-avoidance response (far-red)

3. What technology is best for grow lights?

Grow lights are available in various technologies like LED, HID, fluorescent and even incandescent. Because LED bulbs and fixtures produce very little heat and use less energy than similar technologies, they are considered a great option for grow lights.

LED grow lights also offer the advantage of targeted color spectrums. Fixtures can be tuned to provide exactly what the plant needs, eliminating waste since older technologies generally provide a larger range of colors than needed.

Grow Lights

Some popular options are LED grow luminaires, LED grow strip lights and LED grow flat panels. These lights come in a multitude of configurations to work for various spaces, like cloning racks, vertical farms, large commercial vegetation tables and much more.

Grow lighting has many components and the recommended lights will depend on the type of plants and the growth goals for these plants. Lighting Supply offers are large selection of grow lights, grow bulbs, grow fixtures and many accessories.

Not sure where to start? Call our friendly customer service team today at 800-609-5790.

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