A common misconception amongst indoor growers is that light leaks during the vegetative growth phase won't disrupt crop growth. However, any irregularities in lighting patterns can stress plants out.
What's more, the switch from an 18hr veg cycle to a 12 hr flowering cycle signals to plants to switch to flowering. Any light leaks after the switch can disrupt this and put plants back into vegetative growth. You may even get genetic abnormalities in some species of plants.
Even though plants are in their bloom stage and thrive off the "RED" light emitted by the Bloom mode they still require some blue and green light to really thrive. Always have both switches ON (VEG and BLOOM) once you plants are in the Blooming stage.
Vegetative
The vegetative light cycle of cannabis is when plant growth truly takes off. Much like a human adolescent, the plant will achieve most of its vertical growth during this time. Lasting between 3 to 16 weeks, the vegetative stage requires full-spectrum light for 18 hours and 6 hours of darkness.
Light Leaks are More Dangerous than You Think
A grow room experiencing light leaks can confuse the plant into thinking it's not yet time to flower, which stresses the plants and can create hermaphrodites at worst. At best, it can still stress plants out and reduce the end yield of your harvest.
Light leaks are more common for long exposure photography. That means that it's less likely you see them when using 'normal' shutter speeds. If, however, you see them for all your images, that's an indication that your lens or camera is damaged.
A: In general, you should not leave grow lights on 24/7. Plants need a light-dark cycle to develop properly. It's believed that they truly do “rest” during periods of darkness, and probably use this time to move nutrients into their extremities while taking a break from growing.
Telltale Signs of Too Much Light
The most apparent sign is leaf burning. This typically causes the yellowing of leaves at the top of the plant but the veins stay green, and the leaves take on a yellow or brown, burnt look.
You can remove fan leaves during flowering in much the same way you do during veg. Prune away large leaves that are overshadowing bud sites, as well as dead or dying fan leaves. One thing to keep in mind is that you should prune in intervals, giving at least a couple weeks between each session.
The advantages to using a single, full-spectrum LED grow light for both vegetative and flowering lifecycles include: Plants don't experience shock when changing spectrums. When plants grow leaves, they optimize the leaves for the light they are currently receiving.
In the vegetative stage, LED grow lights should be between 12-24 inches away from the top of the canopy. During this stage, more light is needed for photosynthesis, so the light source should be located closer to the plants. As the plants progress through the flowering stage, their demand for intense light decreases.
Once you decide on your vegetative timetable, it is time to think about how you will switch the light cycle. This plant has been in flower for two weeks and displays young, white flowers. Most growers use an 18-hours on/6-hours off light cycle for the veg phase. Some prefer to use 20 on/4 off, which is also acceptable.
Common Causes for Yellow Cannabis Leaves During Veg
Most commonly, the yellowing of leaves on the lower fan leaves is due to a lack of nitrogen. However, this does not always mean the grower is not supplying the garden with adequate nitrogen.
Blue light is essential for both the vegetative and flowering stages of plant growth, but mainly for establishing vegetative and structural growth.
If you're planning on growing veggies, a full spectrum light with a color temperature in the blue range (5,000 – 7,000K) is recommended, and for fruits and flowers, the red range (3,500 – 4,500K) is the guiding light.
Light burn may also cause loose and airy buds. That's because the excess light causes nutrient deficiencies as plants struggle to overcome their heat and thirst. Fortunately, you don't have to wait for these symptoms to emerge to know whether greenhouse lighting is too strong.
Photoperiod cannabis plants kept in the vegetative stage will continue to grow. So if you veg them for too long and don't control it, they will grow very large and unwieldy. Some strains of cannabis like to grow tall and spindly—for instance, landrace sativas.
UVA and UVB radiations are present in the sunlight and the light produced by LED grow fixtures. These two types of radiation are dangerous to humans. They can also cause various skin diseases, including skin cancer.
Most LED grow lights you can find today are “full spectrum” lights, which is sort of a buzzword that means you can use them for vegging and flowering.
Increased light duration allows the plant to make sufficient food to survive and grow. However, plants require some period of darkness to properly develop and should be exposed to light for no more than 16 hours per day. Excessive light is as harmful as too little..
Continuous Lighting Promotes Plant Growth, Light Conversion Efficiency, and Nutritional Quality of Eruca vesicaria (L.)
Even if a leak is small, water may find its way into light fixtures and other electrical wiring. In most cases, this will cause a harmless short, but it can sometimes result in sparks that provoke a deadly blaze. For this reason, homeowners should act quickly if they notice water in or around any lights or outlets.
A leak near a light fitting is a serious electrical hazard. Water acts as a very good conductor of electricity and the following immediate risks exist: Risk of a potentially damaging and life-threatening electric shock. The risk of fire – water can cause sparking and shorted wires which can start a fire.