Nursing Cannabis Seedlings

Now where were we? That's right, as mentioned earlier cannabis seeds usually grow above the medium about 24 hours to 96 hours from the moment the (sprouted) seed was placed in the medium. These baby cannabis plants, which have a stem and two cotyledons, are now called cannabis seedlings. In this edition of my column I'll elaborate further on taking care of seedlings. 

 Inside the Cannabis Seed ASC Germinated Cannabis Seed


Seedlings are delicate cannabis babies that require a lot of love, attention, patience, water, warmth and light. That's right, it's a whole laundry list, just like a real baby! But with seedlings it's fair to assume that just one mistake (like not enough water, no light, temperature too high/too low) is fatal, then a seedling will die, so mistakes cannot be permitted. From the moment a seedling grows above the medium the seedling phase begins (which is part of the vegatative phase). But then you're not there just yet, because in these few primary weeks of the vegatative phase it's of the utmost importance that the seedling has at all times access to:

  • direct light; seedlings grow towards the light, the more direct the light is the less the seedling has to 'stretch' towards it, so it stays more compact and you prevent the stem from becoming long and flacid which could cause it to break.
  • 24 hours of light in the first two weeks since the beginning of the sprouting process above the medium, then 18 hours of light and 6 hours of darkness: 18/6 light schedule.
  • water
  • a temperature between 20-25 degrees Celsius
  • huminity > 70% for the first 2 weeks, then >60%
  • nutrients (grow fertilizer)

When leaving out one or more of the factors mentioned above, the viability of the cannabis seedling will decrease. In other words, there is a great chance that the seedling won't survive. 

Cannabis Zaailing @EsjeHerb


As mentioned previously, seedlings are very sensitve to their surrounding factors. When there is not enough direct sunlight the seedlings will begin to stretch and attempt to reach the light this way, this is undesirable. The light has to come to the seedling instead of the other way around. Then the internodes of the seedling will stay close together, it also promotes the sturdiness of the stem. Therefore always make sure the seedling stays in:

  • direct sunlight (never in the shade, in connection with stretching) or
  • direct LED-light or
  • direct T5 Fluorescent light
  • direct HPS light (note: HPS light in the first two weeks after sprouting is not recommended because HPS emits a lot of heat and the light is very strong. When HPS needs to be used, do not place the seedlings too close to the light source and make sure the huminity level stays above 70% to prevent seedlings from buring/drying out. 

CannaBabies under t5 light CannaBabies under LED light 


The development of the root system of a seedling is essential for the process of a healthy growing and blooming phase. Therefore always make sure that the seedling transpires as less as possbile, and rather uses this energy for growing and developing its root system. But how can you ensure that a seedling hardly transpires? Make sure that there's enough huminity in the air, a high huminity level is essential in the vegetative phase. Keep the huminity level between 70-80% in the first two weeks, and then ensure a huminity level of at least 60% after that.

* Transpiration: Cannabis plants transpire for a number of important reasons, such as regulating their own temperature, to transport important minerals and nutrients to the plant cells (osmosis) and obtaining carbodioxide from the air. By transpiring the plant is able to cool itself, and water will leave the plant so more water can be absorbed by the roots (by means of osmosis). When transpiring the plants open their stomata so that water is able to leave the plant and CO2 can be absorbed.

Cannabis Leaf Details ASC

Depending on the medium you use, also the pH-level of the medium and feeding water need to be closely watched. Nutrients that ended up in the medium via watering can only be absorbed by the roots of the plant within certain pH-levels. The ideal pH-levels for cannabis plants are between 5.5-6.5 (hydro/coco) or 6.0-7.0 (soil).

Cannabis Roots @EsjeHerb

Cannabis roots grow in response to depletion zones (watch the documentary  “What Plants Talk About” to see a very interesting video about this ). This means that the roots grow 'outside', looking for water and food. When a root has absorbed all the available water and nutrients in a particular area of the growth medium then it will go on to another area of the medium. It will continue to search for water and nutrients. This is how the cannabis plant fills up the growth medium eventually entirely with roots. 


THE GROWING PHASE (Vegetative Phase)

After the first 2 weeks of the seedling phase (vegetative phase) starts the most important part of the vegetative phase. This is also called the main growing phase, or the 18/6 period, because during this phase the plants are only growing in preparation of the blooming phase. Do you want to know more about the blooming phase, then keep a close eye on my next column... Happy Growing!