GROWING WITH LED: WHAT TO CONSIDER FOR EACH STAGE OF CULTIVATION？
As we touched on earlier, many types of LEDs have a fixed light spectrum that works for both the vegetative (growing) and flowering phases of cannabis. This way, you can just use the same light throughout your entire grow from seed until harvest.
Although this is convenient for most, there are those who want to fine-tune their lights for best results and optimal efficiency in each growing phase. For this purpose, some commercial LED lights have a switch to activate a veg light spectrum or a flower light spectrum. Here are some more factors to consider throughout each stage of growth.
（A） LED LIGHTS AND SEEDLINGS
As soon as your seeds have sprouted, your soon-to-be cannabis plant will need light to grow. Compared to more mature plants, however, your seedling is much more sensitive to intense light. Because of that, you should be careful when starting out with strong LEDs.
If your LED has a dimming option, turn your light to a lower intensity. If this isn’t an option, consider moving your lights further up, away from the seedling. On the other hand, ensure that you do not move the lights too far up, as this could cause the seedling to grow spindly and lanky.
Likewise, if your LED has a switch to activate either a vegging or flowering spectrum, set it to veg, where the light normally emits a “cooler” blueish light, which is optimal for this stage. Set your timer to 18 hours of light per day, with 6 hours of darkness.
As your seedling grows taller, stronger, and approaches the most robust part of the vegetative growing stage, you can then gradually increase the light intensity.
（B） LED LIGHTS DURING VEGETATION
Set your light to 18 hours per day and 6 hours of darkness. Some growers choose to grow with 20–24 hours of light to maximise vegetative growth.
Monitor your plant’s development; if all goes well, it should grow healthy, strong, and bushy. If it grows lanky and spindly instead, this is likely because your plant is not getting enough light. Increase the intensity by lowering the light toward the plant canopy or turning up the intensity using the dimmer if your light has one.
How long you want to veg your plant will normally depend on how much space you have available. You can technically let your plant grow under 18–24 hours of light as long as you want, but there will likely come a time when you want to switch to flowering, as the plant would otherwise simply grow too big. Know that some cannabis strains can stretch considerably (up to 2x or more) during early flowering. Take this into account upon deciding when to initiate the switch to bloom.
（C） LED LIGHTS FOR FLOWERING
Photoperiodic cannabis starts to flower in late summer when the daylight hours naturally begin to diminish. Indoors, the grower is responsible for inducing bloom by setting the light schedule to 12 hours of light and 12 hours total darkness. If your LED light has a flowering switch, turn it to flowering mode.
When you flower indoors on a 12-12 schedule, it is important that the 12 hours of darkness are not interrupted. So make sure that your tent or greenhouse doesn’t have any light coming in from outside. This would otherwise revert your flowering plant back to veg or potentially cause other issues such as hermaphroditism.
If your LED has a dimmer, now is the time to turn your light to its maximum intensity, or lower your light to the recommended distance from your plants for the flowering stage. If you are not sure what this distance is, most grow light producers have recommendations available.
Important: if you change anything with your lights, such as when you increase intensity and/or lower their position, make sure to do so gradually over several days, rather than in one go. Too sudden of a change can stress your plants too much.