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Does it help to use only blue light at the end of flower cycle?

end of flower cycle

The end of the flower cycle may be toward the end of the growth cycle, but that does not mean your yield’s quality is set in stone. It’s no secret that light spectrum can affect everything from a plant’s smell to its appearance and tweaking light exposure at the tail-end of flowering can have dramatic effects.

Blue light is vital for plant growth, and experienced growers recommend using blue light at various points in the grow cycle. Some growers recommend increasing blue light exposure – sometimes exclusively using blue lights – at the end of the flower cycle.

Does it help to use only blue light at the end of the flower cycle? Like most questions involving spectrum control, there is no single answer, and a lot is contingent on what types of crops you’re hoping to produce.

Below, we’ll break down how blue light affects plants and what increased levels of blue light can do at the end of the flower cycle.

Which Grow Lights Include Blue Light?

Both HID and LED lights can include some blue light during the growth cycle. Metal Halide lights are famous for high levels of blue light and are often used during the veg cycle for shorter, bushier plants and for better smells and colors at the end of the flower cycle. HPS lights have very little blue and are mostly used in the main part of the flower cycle to develop maximum yields. LED lights, however, can vary the spectrum for maximum control of grow results in both veg and flower.

What does that mean? With an HID light, you have to switch the bulb at various points during the grow cycle to change light spectrums to get higher or lower levels of blue. However, LED fixtures have variable spectrum capabilities. This means that, with a single fixture, you can switch between various light spectrums. This is a big reason LED lights have become increasingly popular for indoor growers.

When Is The End of Flowering Stage?

For cannabis, there are varied grow periods depending on the strain and the desired size of the plants.

For auto-flowering strains, the entire growth cycle is fixed by the plant’s genetics. Regardless of the light levels or daily hours of light, these plants will go through their growth cycle from beginning to end in roughly 60 to 90 days. This varies with different strains and you may need to experiment with a strain before you know when to harvest.

For nonauto-flowering strains, plants will stay in veg and will only start flowering when the daily light period gets close to 12 hours a day. Here, indoor growers can choose how long they want the plants to remain in veg and how big the plants will be when flipping over to flower.

Once plants have been flipped over to flower, most strains will be ready to harvest in roughly 8 to 10 weeks. This varies a lot by strain, so you’ll have to look up specifics to estimate the number of weeks before harvesting. Not only that, every plant grows at its own pace. Pay attention to how your plants are developing to gauge when they are ready to harvest. In most cases, late the final flowering phase will be 6 to 8 weeks after flipping over to 12-hour light periods. This is the time when the introduction of more blue light can have a positive effect on smalls, colors and chemical profiles.

What Is Blue Light?

Light spectrum affects your crops the moment your plants start growing. Different color lights on the spectrum all have a unique effect on plants.

  1. Blue light is a short, high frequency wavelength that occurs naturally in nature. During spring and early summer, when plants are usually in their vegetative stage, there is a lot of blue light outdoors. In late mid to late summer, blue light diminishes, and more red light becomes more prevalent. In late summer and fall, the red light diminishes once again and the ratio of blue again increases.

Therefore, blue light is one of the most important lights for vegetative growth, and most growers recommend blue light during the earliest grow stages. Blue light has a massive effect on chlorophyll formation, which helps plants absorb light. This promotes leafier plants with shorter stems – desirable traits in veg but not so much in flower.

Because it helps with so many mechanisms that are vital to plant health, blue light is used in some amount throughout the entire growth cycle. This includes the end of the flower cycle as well. However, if you want to use high levels of blue light – or exclusively blue light – it can have profound effects on your final yield.

Is it beneficial? The answer to that question depends on what kind of flowers you’re hoping to create.

Should I Use Blue Light At The End of Flower Cycle?

It’s no secret that lots of blue light is vital at the beginning of the grow cycle, but what about the end of it? During the end of the flower stage, blue light can affect plants in several noticeable ways.

During the final three to seven days of the flowering stage, some growers increase their blue light levels dramatically. This can potentially increase terpenes by 50% while also increasing cannabinoids.

Higher cannabinoids make your crops more potent, which could increase their market value. Terpenes, if you’re unfamiliar, are strong-smelling oils that affect both a plant’s fragrance and taste. Not only do terpenes make plants smell stronger, they can add a distinct taste like berry, mint, and pine to your plants.

Experimenting with varying levels of blue light toward the end of the flower cycle results in different tastes and smells, so it takes some trial and error to get your desired results. This is often how growers create unique strains.

So, should you use blue lights at the end of your flowering cycle? To some degree, yes, almost always. However, how much blue light you should use – and for how long – depends on what you’re trying to create.

Again, a lot comes down to experimentation. There’s no precise formula to get a certain taste or smell, and that’s part of the fun of full-spectrum lights. They allow you to try out different combinations of light at various points in the growth cycle, ultimately giving you the freedom to custom create your own unique plants.

The Bottom Line

Every grower wants to accomplish something different, so how much blue light you use – and when – is a personal choice. You should always use some degree of blue light, especially during the vegetative phase, as it’s extremely important to plant growth. However, upping your blue lights at the end of the flower cycle is optional.

Increasing blue light while your plants flower can definitely change the taste, smell, and potency. It’s a very effective technique for growers hoping to create unique strains. LED lights give you the most convenient control over the light spectrum, allowing you to switch between varying colors without changing a bulb.

If you’re looking for variable spectrum lighting, our SolarSystem series provides variable spectrum control with a digital controller which allows you to experiment with a wide variety of different spectrums and grow strategies.

As always, we’re happy to help if you have any questions about light spectrum, growing, and more. Feel free to reach out here for more information.


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