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How to Choose the RIGHT Spectrum for Your Plants

How to Choose the RIGHT Spectrum for Your Plants

Are you struggling to figure out the best light spectrum for your plants? You're not alone—many growers feel overwhelmed by the options. In this review, we'll simplify what you need to know to choose the perfect spectrum for your indoor garden. Discover how different wavelengths can supercharge your plants' growth, from seed germination to flowering and learn about the different types of LED grow light spectrums. Get ready for practical tips that will make your plants thrive like never before!

Understanding Light Spectrum

To begin, let’s quickly dive into the main wavelengths in the light spectrum and their importance in plant growth. The spectrum includes UV, blue, green, yellow, red, and far-red wavelengths, each playing a unique role:

  • UV Light (< 400nm): Though limited in use, it enhances traits like pigmentation and defense mechanisms.

  • Blue Light (400-500nm): Essential for vegetative growth, encouraging bushy and compact development.

  • Green Light (500-600nm): Least absorbed but penetrates the canopy to support photosynthesis in deeper leaves.

  • Red Light (600-700nm): Crucial for flowering and fruiting, promoting stem elongation and blooming.

  • Far-red Light (700-800nm): Influences germination, flowering, and shade avoidance responses.

Plant Growth Stages and Light Needs

Understanding the light needs of plants at various growth stages is crucial for optimizing their development. Different wavelengths of light play specific roles during each phase of growth. Keep in mind that with the following, there is some wiggle room with the proportions of wavelengths so I will be speaking in generalities here.

Seedling stage

During the seedling stage, plants benefit most from blue light with a small amount of red light. Blue light supports strong root development and prevents seedlings from becoming leggy, ensuring they grow into sturdy plants. The addition of some red light helps initiate early growth processes, but you shouldn’t add too much red light in this stage.

Vegetative stage

In the vegetative stage, you can add a bit more red light while keeping a high proportion of blue light. Blue light is essential for promoting robust leaf growth and keeping plants compact and bushy. The presence of red light assists in overall plant vitality but should remain less dominant. 

Flowering / fruiting stage

During the flowering and fruiting stage, plants need a higher proportion of red light to stimulate flower and fruit production. Red light encourages stem elongation and the development of flower buds, while blue light continues to support overall plant health and quality. Excessive blue light during the flowering stage can lead to a reduction in flower sites and weaken flower development. 

Types of LED Grow Lights

Understanding your plants' specific light requirements for each growth stage will help you choose the right LED grow lights for your garden. There are three main categories of LED grow lights: full spectrum LEDs, targeted spectrum LEDs, and adjustable spectrum LEDs. Each type has its own advantages and is suitable for different growing setups and goals.

Full Spectrum LEDs 

Full Spectrum LEDs mimic natural sunlight by providing a broad range of wavelengths that cover most, or all, of the light spectrum. These lights are versatile and can be used throughout all growth stages, from seedlings to flowering. Full spectrum LEDs are particularly beneficial because they simplify the lighting setup, eliminating the need to change lights as plants progress through different stages. 

Most brands offer LED grow lights with a well-balanced spectrum that includes a healthy amount of blue, green, and red light. While some brands might feature a slightly higher proportion of blue or red light, they generally avoid extreme imbalances. Additionally, some brands incorporate UV and infrared diodes into their lights to further enhance plant quality and morphology.


However, a drawback of full spectrum LED grow lights is that their spectrum is fixed and cannot be adjusted. This can be limiting because a full spectrum LED may not be ideal for all growth stages. For instance, seedlings may benefit from more blue light, while plants in the flowering stage might require increased red light. The inability to tailor the spectrum to these specific needs is a notable disadvantage of full spectrum LEDs. One way to address this limitation during the flowering stage is to add supplemental red light.

Targeted Spectrum LEDs 

Targeted Spectrum LEDs are not just the infamous blurple lights, which include only red and blue diodes. Instead, they use full spectrum white diodes to achieve a near-complete full spectrum, but with a higher proportion of specific wavelengths tailored to particular growth stages. For example, blue-heavy lights are ideal for the seedling and vegetative stages, while red-heavy lights are better for the flowering stage. These lights are highly efficient in terms of energy use and photosynthesis, maximizing plant growth during specific phases.

The main disadvantage of targeted spectrum LEDs is that growers may need to invest in multiple types of lights to cover all growth stages. Depending on their goals and setup, they might need separate rooms for vegetative growth and flowering, each equipped with its own specific lights. This contrasts with growers who use full spectrum, non-targeted LED grow lights, which can be used for both vegetative and flowering stages.

Adjustable Spectrum LEDs

Adjustable Spectrum LEDs offer the best of both worlds by allowing growers to customize the light spectrum according to their plants' needs. These lights can be adjusted to emit different wavelengths at different stages of growth, providing flexibility and control. Adjustable spectrum LEDs are highly versatile and can be particularly useful for growers who want to fine-tune their lighting setup for optimal plant health and yield. While these lights can be more complex to use, their adaptability makes them a valuable tool for serious growers. Due to the additional drivers required to separate the spectrum channels, they generally come at a higher cost compared to other types of LED grow lights.

Practical Tips for Choosing the Right Light

1. Plant Requirements During Different Growth Stages

Consider the specific requirements of your plants at different growth stages, whether it's for seedlings, vegetative growth, or flowering stages. For example, are you growing leafy greens that would benefit from a full spectrum, higher in blue light? Or are you growing larger plants like tomatoes, peppers, or cannabis, that may benefit from a warmer spectrum during fruiting or flowering? Keep in mind that the different plant varieties may respond differently to the same spectrum.

If you're unsure about which spectrum to choose, a balanced full-spectrum LED will meet your needs 95% of the time, regardless of the plant types you are cultivating. Most LED grow lights fall into this category.

Recently, UV and Far Red (also known as Infrared) light has become quite popular, with more growers seeking these wavelengths in their lights. A small amount of UV light is beneficial for most plants, as is some Far Red light, but too much UV can damage your plants, and too much Far Red can cause them to become leggy. Since white light diodes contain some Far Red, nearly all LED grow lights include a bit of it. If you want to add or boost UV or Far Red wavelengths during the fruiting or flowering process, you can find supplemental UV and Far Red bars on the market to use alongside your primary light.

2. Budget

Factor in your budget constraints to ensure a cost-effective choice. LED grow lights come in a wide range of prices, so it's important to determine how much you're willing to spend. Keep in mind that higher initial costs for more efficient, durable, and advanced lights can lead to savings in the long run through reduced energy consumption and longer lifespans. However, there are also many affordable options that provide excellent performance for smaller or less demanding setups. These typically include fixed spectrum lights, and not adjustable spectrum lights. Balancing cost with quality and functionality will help you find the best light for your needs without overspending.

3. Research and Reviews

Next, engage in thorough research and reviews. Look for credible reviews and recommendations from experienced growers. Compare spectrum specifications and user feedback to understand the performance and suitability of different lights.

4. Manufacturer Support

Lastly, consider the manufacturer support when selecting a light. Opt for brands known for providing good customer support and warranty options. Check for additional resources such as grow guides or online communities to assist you in optimizing your growing experience. And, of course, you can reach out to us here for assistance on finding that perfect light!


To sum this up, choosing the right LED grow light spectrum is crucial for maximizing plant growth and yield. Consider your plants' specific needs at different growth stages, such as seedlings, vegetative growth, or flowering, and choose a balanced full-spectrum LED if unsure, as it covers a wide range of plant types. Factor in budget constraints, conduct thorough research on spectrum options, and prioritize brands with strong manufacturer support.

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