Raising Germinated Autoflower Seeds in 50/50 Perlite/Vermiculite Mix

Germination Method: Moist paper towel in sealed container sitting in warm spot (90% success rate - "if it ain't broke, don't fix it")

Refusal to Transplant: Attempting to transplant autoflower seedlings using plastic/coir cups has caused issues for me in the past. Apparently when the tap root hits the bottom of the cup it decides to give up on further growth. For this reason I am hoping to overcome the issues associated with planting a germinated seedling directly into the final growing medium.

Planting Method: After 48 hours of germination when tap root is approx. 1cm long, the seedling is placed in the pot with perlite/vermiculite mix (root down, seed 5mm below surface).

Failed Attempt #1 - Growing Medium Saturated

• An hour before planting the germinated seed, I fully saturated the mix and drained the excess water.
• The seedling seemed to enjoy this at first, guickly shooting up the stem with cotyledons and true leaves.
• However, per the image below, this is where the growth stopped. After the below image was taken, the cotyledons quickly turned yellow and true leaves browned (notice the tips on the second true leaves browning) - the seedling was drowned.
• As hard as I tried I could not dry the perlite/vermiculite mix out quickly enough. The vermiculite holds moisture so effectively that even if I had soaked the mix a week before planting I do not beleive that it would dry out quickly enough to prevent drowning.

Failed Attempt #2 - Growing Medium Too Dry

• Instead of saturating the growing medium, this time I only lightly watered the whole top layer with 100ml of 1/4 strength nutrient mix, then planted the seedling.
• Every 4-5 hours, when the top layer of the mix had become only slightly moist, I watered again with 100ml of 1/4 strength nutrient mix.
• I thought that I had not let the mix dry too much at any stage, however after a couple of days when the stem had failed to emerge, I carefully sifted through the top layer to find that the seedling had not grown beyond the point when I had planted it and had shriveled! (I was too annoyed to remember to take a photo sorry)

Attempt #3 - Propagation Dome (To be continued...)

• This time I will again not saturate the mix prior, yet double the watering amount to approx. 200ml of 1/8 strength nutrient mix, and will also place a propagation dome over the pot. Hopefully this will provide enough moisture to the mix (yet not too much to drown the seedling) and slow the drying rate, but also maintain a high-humidity level to help the seedling thrive.

Comments/suggestions welcome!

Post Update - 14th September 2022:

Attempt #3 Continued - Propagation Dome - SUCCESS!!

• With great relief I can report that this method worked!
• However, I would not say that it was primarily due to the use of the propogation dome. In my opinion, the success of this attempt can largely be attributed to simply acheiving a suitable level of constant moisture (i.e. not saturating the mix prior, yet watering lightly and regularly).
• The successful watering regime consisted of:
  1. Evenly distributing approx. 100ml with a watering can where the seedling was to be planted.
  2. Planting the seedling, lightly covering with perlite/vermiculite, then watering a further 50-100ml above and around seedling placement.
  3. Placing a propagation dome over the pot.
  4. Within as little as 24-hours the seedling breached the surface.
  5. Every 8-10hrs lightly watering with approx. 50-100ml above and directly surrounding the sprout.

A few important notes:

• Whilst the propogation dome may help to retain moisture when the seedling is first planted, once the sprout is pushing up its first true leaves I would recommend removing the dome entirely and then simply maintain constant light watering from that point on. Leaving the dome in place beyond this point I feel may risk trapping moisture in for too long potentially stunting the growth of the sprout.
  
  
• Avoid using rockwool or peat pellets in the perlite/vermiculite mix - I feel like this needs to be stressed more by seed producers; autoflower seedlings are EXTREMELY sensitive! (much more than photoperiods) I have had so many autoflower seeds just give up on further growth when their roots grow through one medium to another. From my own experience, my strong advice is to always plant sprouted autoflower seeds directly into their final pot and grow medium to avoid any possible root growth stress.
  
  
• A regular old saucepan lid will work just as well as a propagation dome