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Marijuana Growing Lights

Scientific studies have shown that certain light spectrums can be beneficial for growing weed and its cannabinoid content. The highest amount of THC in weed flowers was achieved by using NS1 and AP673L LEDs, whereas HPS (high pressure sodium) lamps produced the worst results.

When Do Marijuana Plants flower under LED Lights?

Under natural conditions marijuana generally begins flowering with the onset of fall, when days become shorter. This is the idea behind all the techniques of growing weed under led lights — you basically emulate natural light cycles.

Cannabis growing is divided into five stages: seed, seedling, vegetative, flowering, harvesting. During the vegetative stage, you’ll have to set the light cycle to at least 18 hours of light a day. Some growers prefer to go as far as 24 hours a day.

It is not really light that makes all the difference, but darkness. The lengthening of uninterrupted light exposure tells cannabis to begin the flowering stage.

Growing Weed under LED Lights

What kind of light is better to grow weed? LED lights are a truly useful invention. When growing marijuana you need:

  • Violet-blue light (400-520 nanometer range) to enhance growth, chlorophyll absorption, and photosynthesis.
  • Red light (610-720 spectrum range) for blooming and budding.

The light spectrum for growing weed can be switched to the desirable one in most types of modern LED lamps.

How High Should LED Lights Be Placed?

Approximately, incandescent grow light bulbs should be no lower than 24 inches above your plants. LED and fluorescent lamps have a lower heat signature, so it’s okay to put them 6 and 12 inches above plants respectively.

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Marijuana leaves that start wilting and turning yellow can be either a sign of nitrogen deficiency or light burn. If the latter is the case, then widen the distance between your plants and the lights.

Growing Weed with T5 Lights

Fluorescent (T5) lights are not the best option for growing weed. Usually, they merely don’t have enough capacity to provide cannabis with enough light in the flowering stage. Though, as lighting for cannabis seedlings they are just fine.

Turning Lights Off to Make Cannabis Flower

Cannabis plants have two key types of light spectrum receptors: red phytochromes and phytochromes of the far red spectrum. Under sunlight or a LED lamp, their number is balanced. But at nightfall, the far red receptors begin to turn red. If the dark period is long enough, most of the receptors turn red. At this moment, the flowering of photoperiod cannabis begins – this is how its biology works.

Due to this, photoperiodic strains of marijuana grown outdoors are in the vegetative stage throughout long spring and summer days, starting to bloom only at the end of the summer when days become shorter. Most photoperiods growing outside begin to flower at 13-14 hours of daylight.

In order to make your plants bring forth juicy buds full of THC, your LED grow lights for weed must be turned on for no more than 12 hours, i.e. 12 hours of darkness and 12 hours of light is most of the time the optimal regime for the flowering stage.

Indoor growers use various regimes of light and darkness, such as 18/6, 20/4, or 24/0 in order to prevent the phytochrome red receptors from dominating too quickly, thereby slowing the onset of flowering. In fact, while maintaining long daylight hours, the hemp plant can remain at the vegetative stage indefinitely.

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On the other hand, many growers try to accelerate the onset of cannabis flowering by leaving the plants for a day or two in complete darkness. This way flowering happens thanks to the rapid accumulation of red phytochromes over a long period of darkness.

Effects of Darkness and Light on Cannabis Seeds

Regardless of which type of marijuana you have chosen, it is required to observe the alternation of the light period to maintain darkness. Photoperiods are highly dependent on the length of the dark period of the day, while autoflowering cannabis varieties do not experience any strong correlation with light cycles.

However, autoflowers also need a change of day and night. By and large, light and darkness are equally important for cannabis plants.

When growing new marijuana plants, you must first germinate the seeds. Provided one thing – darkness. Cannabis seeds need darkness to germinate. Ideally, germination should take place in an enclosed space within 2-3 days. It is recommended that you use the simple and reliable method of damp paper towels.

It is total darkness that stimulates the splitting of the seed coat and the appearance of the root. As soon as a small white root becomes visible, it is time to carefully move the seed into the substrate for growing and put into the light. In the wild, cannabis seeds drop from inflorescences in the fall and are stored in the soil. With the onset of the spring, only those seeds that were not buried in the ground too deep, and were not exposed to light, manage to break through the top layer of soil.

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Violation of Cannabis Light Cycle

Keep in mind — lighting for cannabis plants must be turned off at night during the flowering stage. In no case should you interrupt the dark part of the light cycle. Light in your greenhouse at night will inevitably lead to stress. If your plants need inspection at nighttime, a special green light must be used. The arrival of light at night can adversely affect the health of autoflowers, notwithstanding their high resistance to stress.

Unwanted light can hinder flowering, or, in the worst case, it can cause hermaphrodite plants. Moonlight is not dangerous for cannabis, but this is the only exception. Even using a mobile phone as a flashlight may be enough to interrupt the dark cycle and cause irreparable harm. Therefore, the main rule is – the night should be completely dark.

Do you want to know all cannabis growing tips and tricks? Read our Growing Guide right now!