For many indoor cannabis growers, and especially those who grow hydroponically, “Granny’s method” (or the airing cupboard means) does not suit either their style (that of creating a scientifically controlled environment) or their growing medium (rockwool). To provide the optimum conditions for marijuana seed germination, it is important to:
- Give the seeds the correct temperature for germination. This can be done using a heated propagator, where the mat is placed under the seed medium. Optimum temperature is 21-25C for seed germination. Note that strains which are heavily sativa based need a higher temperature (up to 5ºC warmer) to germinate. This reflects the warmer climes that they originate from.
- Most popular mediums for seeds to go on to hydroponic use are Jiffy Peat Pellets, small Grodan rockwool cubes Soak first in pH neutral water, squeeze out to remove excess moisture then make a small dent at the top of the medium (about 0.5cm deep) to receive the marijuana seed.
If you are going to grow hydroponically, use the rockwool cubes.
- Maintain humidity and thereby residual moisture levels in the propagator by leaving lid on, and checking twice daily. Always underwater with pH neutral water rather than from above. This helps minimize disease and prevents accidental washing away of the newly emerging seedling. Drier areas of the medium will absorb upwards the water whilst at the same time the tap root is encouraged to make strong downward growth.
- Avoid overwatering – do not let the medium stand in water as it will prevent air absorption which is vital for the seedling
- Keep in these conditions until the serrate leaves appear – these are the “true” leaves, not the first two round cotyledon leaves.
- temps: 21-25
- humidity: 85%
- water: pH 5.8
To use this means of germinating cannabis seeds, you will need:
- Heated propagator
- Rockwool Cubes or Jiffy Pellets
- PH PEN & calibrating fluid
If you are taking growing marijuana seedlings seriously, and know that you are going to be producing crops rotationally, it might be worth investing in a propagation tent. Read our review of 2 of the best here