Spectrum creates distinct effects: Blue light produces more compact, resilient plants with higher nutrients, while far-red encourages faster expansion and growth rate.
Applications matter: While MBG Marketing uses tunable lights for their blueberry breeding program, most growers benefit from simpler, fixed spectrum solutions designed for their specific crops.
Consider key factors: Light source dominance (how much light is from the sun vs. LEDs), sales value of plant quality attributes, crop-type consistency, and growers' technical capacity all determine if spectral manipulation is worthwhile for your operation.
Start small: Test different spectrums in a small section before major investments, and work with experienced lighting partners who understand the nuances of your specific growing situation.
The science of light spectrum and its effects on plant growth has evolved dramatically over the past decade. For greenhouse growers seeking to optimize their crops, understanding when and how to manipulate light spectrum can create opportunities—but navigating this complex field requires balancing multiple factors. Let's explore what's possible, what's practical, and how to determine the right approach for your specific growing operation.
Understanding spectrum impacts on plant growth
The fundamental tradeoff when changing light spectrum is quantity versus quality—compactness versus expansion, secondary metabolite production versus raw biomass. Different parts of the spectrum create distinct effects on plants:
Blue spectrum produces less total biomass, but creates more compact, thick plants with higher secondary metabolite concentrations. These compounds (like anthocyanins and other antioxidants) enhance nutritional value, taste, and coloration, while improving stress and pest resistance.
Far-red spectrum encourages expansion/extension, helps plants fill growing space faster, and increases overall growth rate by triggering shade-avoidance responses.
Full, balanced spectrum most closely mimics natural sunlight, providing the benefits of both blue and red wavelengths without extreme morphological changes. TotalGrow's standard spectrum fixtures offer this balanced approach, which works best for most applications where extreme plant manipulation isn't necessary.
More often than not, the blue side of the spectrum will produce more compact, thicker plants with better transplant quality and shipping durability. This is especially important if you're growing plants that will be moved or transplanted before reaching their final growing location.
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Real-world applications: From research to results
At MBG Marketing in Michigan, North America's largest grower-owned marketer of blueberries, we recently installed 64,000 watts of energy-efficient LEDs with far-red and blue spectrum tuning capabilities. Because they grow hundreds of different crosses for customers across the country, having a tunable full spectrum toolbox provides tremendous flexibility.
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In practice, they can use increased far-red during the early vegetative stage to encourage faster leaf expansion, then shift to higher blue light intensity when preparing plants for shipping to growers. During winter months with low natural light, they adjust to a more balanced spectrum to maximize growth while maintaining plant quality. The result? Southern highbush blueberries blooming inside a snow-covered Michigan greenhouse in December, with stronger, healthier plants ready for their grower customers.
At York College in Pennsylvania, we created an educational setup with four distinct light spectrums ranging from pure blue to pure far-red over greenhouse NFT lettuce plants. This experimental approach demonstrates what each spectrum can do at a small scale. This allows students to observe how different light recipes affect leaf expansion, coloration, and nutrient content in real time; ultimately providing a toolbox of strategies to utilize at a larger scale in their future careers.
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When spectral manipulation makes sense for your operation
Not every operation will benefit from advanced spectral manipulation. Several factors increase the likelihood it's worth implementing:
Light source dominance: What percentage of light comes from LEDs versus natural light? The more artificial light dominates, the greater impact spectral changes will have.
Value of secondary attributes: If coloration, quality, or chemical concentrations significantly impact your bottom line, spectral manipulation becomes more valuable.
Crop consistency: The more consistent your crops and genetics, the more finely you can tune your lighting for predictable, optimal results.
Technical capacity: Consider your team's ability to manage additional variables in your growing system.
Budget and incentives: Utility incentives can make advanced lighting more accessible.
Leafy greens, herbs, and microgreens are examples with greater potential for spectral benefits, particularly when red coloration is desirable for visual appeal and nutritional value.
Common misconceptions about light spectrum
Beware of oversimplifications about light spectrum. A persistent misconception based on historic lighting technology is that you need blue light for vegetative growth and red light for flowering. While there's some truth here, it's usually overstated. Both spectrums provide benefits at all growth stages.
Another mistake is treating spectrum as binary rather than considering intensity. Including far-red or UVA in your lighting doesn't guarantee results—the amount matters tremendously. Too little might have little to no effect, while too much could be detrimental.
© Magdalene Mastin
Implementing wisely: A staged approach
If you're considering spectral manipulation for the first time, a measured approach is recommended:
Identify a manageable first step, perhaps testing different spectrums in a small section of your grow space.
Consider whether a fixed spectrum tailored to your specific crops, setup, and environment might be more cost-effective than full tunability.
Work with lighting partners experienced in your crops and growing situation who can share relevant case studies.
As technology advances and costs decrease, spectral manipulation will become more accessible. The key is determining whether the benefits for your specific situation justify the additional complexity and investment. Sometimes the simplest approach—adding more light of the right quality with TotalGrow's full spectrum LEDs—remains the wisest path forward.
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