As promised, here is that thread which details planting and topping of cannabis seedlings.
Let's start with some Sunshine Advance Mix #4 - any peat based seedling starter will do. I just like the Sunshine mix because it offers a lot of things to the grow while still being mild enough for seedlings.
Simply hydrate the Mix and evenly distribute moisture. I usually use warm water and let is sit for a couple of hours - running it through with my hands and crushing all of the clods. (The Mix comes in a compressed bale. You'll have to break it up like coco coir.)
Once hydrated, measure the moistened substrate into 3x3 seedling containers. Do not pack the mix into the containers. A gentle shake will fill any voids. Then level the top with quick sweep of a spoon handle. You may tap the substrate down about 1/4 inch or so to give some breathing room between the top edge of the container and the soil surface.
It is important that you allow the seedling substrate to be light and airy - like with a PF Tek style Brown Rice Flour cake. If it becomes impacted the soil populations will struggle and the seedling will suffer as a result.
Once the substrate is loaded into containers simply use a dibbling stick (chopsticks are handy) to make a hole in the substrate surface roughly 5 times the length of the seed body.
Drop a seed into the newly made hole and gently sweep some loose substrate over the seed. Again - do not pack or impact this seal. Think light and airy. Just enough to cover the seed and prevent light penetration.
Once planted keep the soil substrate moist but not wet. Bottom watering can help so as not to disturb the substrate surface or displace the seed.
Since I'm using T8 flourescent for this project I'll get the containers as close to the lights as I can manage without risking having a sprout touch one of the lamps. Three to four inches of clearance should be fine.
Here are the fast-forward photos showing sprouts emerging from the substrate.
Seeds were planted on Dec. 15th and all of the sprouts had emerged by Dec. 21st.
I have a lower wattage LED grow light coming today which will replace the 400w metal halide fixture I normally use for veg.
Edited by Myc, 25 December 2021 - 11:15 AM.