November 6, 2025
Choosing the right light spectrum for your cannabis grow can make a big difference and impact how your plants develop and much yield you should expect. Here’s a quick rundown of what you need to know.
- Blue light (around 400–500 nm): Blue light helps keep your plants compact and dense. It encourages tight node spacing and healthy leaf development which creates a strong structure to support heavy buds later.
- Red light (around 600–700 nm): Red light creates flowering and bud production. Plants use it to build biomass and increase yields. But be careful! Using too much red light can result in photobleaching.
- Far-red (700–800 nm): Far-red light impacts how plants stretch and when they transition into flower. If used strategically, it can help shape the canopy and slightly speed up the switch from veg to flower.
- Green light: Green light reaches deeper into the canopy which helps lower leaves get fuller. A balanced white spectrum paired with green can make it easier to spot issues like pests or nutrient deficiencies on the plants.
Match the spectrum to what you want to achieve
Vegetative Growth
During the veg stage, your plants are focused on building their foundation with roots, stems, and leaves. This is when blue light really matters. A spectrum with plenty of blue light, along with a balanced white mix, helps keep plants short, strong, and sturdy so they’re ready to support heavy flowers later on.
Flowering Stage
Once you switch to flower, your plants change gears and start putting their energy into bud production. This is when adding red light can be beneficial. Red wavelengths encourage the plant to focus on flowering which helps bud growth, resulting in higher yield. Keeping blue light in the spectrum helps prevent plants from stretching too much and maintains good structure. Adding small amounts of far-red can also be helpful since it encourages even canopy growth and can slightly speed up flowering when used the right way.
Adapting spectrum to your environment
The best light spectrum really depends on two things: your plants’ growth stage and where you’re growing.
In greenhouses, you already have full-spectrum sunlight, which naturally provides plenty of blue and green light. That means you don’t need to double up on those wavelengths — instead, a red-heavy supplemental light can give your plants an extra boost during flowering and help increase biomass. It fills in the red wavelengths that sunlight doesn’t always provide consistently, especially in the early morning, late afternoon, or on cloudy days.
Lights like JumpLights’ ETS MAX 7A, which delivers about 76% red output are great for greenhouses because they work with sunlight, not against it.
Indoor grows are a little different since they rely completely on artificial light. In that case, a more balanced spectrum, like JumpLights’ ETS MAX 5B (57% red), is ideal for supporting strong, healthy plants through both veg and flower. It’s got enough blue and green light for good structure, plus plenty of red to drive yield.
Bottom line
There usually isn’t a one-size-fits-all solution, but certain environments and stages do best with different types of light spectrums. We can work with you every step of the way to help determine what type of lighting solution will work best for your cannabis grow.
