How much light should cannabis seedlings get？

The natural growth cycle of outdoor marijuana(cannabis) is to start life as a seedling in spring, and then “plant growing” in most of the spring and summer, after which it “blossoms” and sprouts to reproduce the next generation. Due to this tradition, photoperiodic cannabis “blooms” when exposed to appropriate dark conditions. If marijuana is given 12 hours of uninterrupted darkness every day, it will bloom (I think it will fall when the night gets longer). Each stage of the life cycle of cannabis plants has its own unique lighting requirements.

Once your seed sprouts (or your clone takes root), your plant is in the seedling stage. This will last only 2-3 weeks indoors, but up to 6 weeks outdoors. At this stage, your cannabis plant will put a lot of effort into developing its roots. As a seedling, your plant will transition from growing single leaf leaves to growing multi leaf leaves (also known as “fingers”) – this indicates that the seedling stage is over.

Cannabis seedlings prefer daytime temperatures of 20 – 25 ° C and cool night temperatures of about 4 – 5 ° C. The high temperature will put pressure on your seedlings and hinder their growth. Although their roots are young and still developing, cannabis seedlings absorb water through osmosis in the leaves. In order to optimize this process, it is important to keep the relative humidity level at 40 – 60%. Humidity levels below 20% can seriously hinder the growth of seedlings and may cause them to develop symptoms similar to certain nutrient deficiencies (yellow or spotted leaves). On the other hand, humidity levels above 60% can cause plants to develop wet spots, leading to withered or rotten leaves and attracting fungi and / or other pathogens and pests. Once your seedlings are in the vegetative stage, you should keep the relative humidity at 50%.

Seedlings are sensitive to light and will burn under strong HID or LED bulbs. Like adult plants, seedlings grow scorched and wrinkled leaves under slight pressure. Or, seedlings that do not have enough light grow tall and thin, and then fall down. For best results, we recommend that you plant your seedlings in the first 10-14 days under 18 / 6 light cycle with CFL grow bulbs with blue light spectrum. Once they grow healthy leaves and at least 2-3 nodes, you can move them to a stronger HID or LED grow lamp to start growing.

In general, the optimal light schedule for seedlings is 18 / 6, which means that the light is turned on for 18 hours and turned off (to make the plants dark) for 6 hours every day. Seedlings can grow well without strong light. Strong light sometimes damages seedlings. However, if you dim the light or use a weak bulb, be sure to check the distance between the bulb and the plant. If the lamp is too far from your plant, it will stretch, and if the lamp is too close, it may burn (especially if it is HID). For example, when using LEDs, you need to keep the lamp between 60-76 cm (24-30 inches) and the seedling.