The substrate looks coarse enough to prevent the roots from rotting on any kind of tree. It looks like something must have gone wrong in the process of repotting the trees, the after care or in the feeding program that caused the roots to give up. It most certainly has got nothing to do with giving too much water. To prevent you from making the same mistakes twice, could you tell us something more of how you exactly repotted and took care of them after so that we can have a better understanding of what may have caused the trees to die?
I received the seedlings about a week after i had ordered them and they were in transit during their shipping for 4 days before i received them. They shipped from new york state in early march. They were packed in damp woodchips and still had a significant amount of clay around their roots. I removed the clay by gentle agitation and light prodding with the end of a chopstick in room temperature water. the seedlings were observed to have fairly obvious root rot on some (the root was swollen and rather squishy) while others had some sort of white fungus and others were fine. The worst offenders were quarantined but all seedlings were potted in a mix of ~60% pummice, ~20% perlite and ~20% potting soil. The soil was added one handful at a time. between handfuls I pushed the soild gently into the roots to fill any gaps. I knew I would be repotting these soon so i didnt make a huge effort to make the soil compact but i tried to avoid air bubbles. I treated the roots with a very dilute solution of hydrogen peroxide (about a 1:100 dilution of .5% hydrogen peroxide for a final concentration of .005% = one capful of hydrogen peroxide in a bottle of water). This treatment was done every other day and the seedlings were watered lightly every day (not because i wanted a schedule but because the soil would dry over the course of the day). About three weeks later, there was still no life but i wanted to move ahead anyway to meet the dealine. the soil was very carefully removed until i got impatient and turned the pot on its side and allowed the soil and trees to slowly pour out. I revoed a bit of the soil with a water bath and carried out my procedure as noted in the previous posts. the seedlings were then potted in a similar mix as before in the same fashion. they were watered every day as before.
Maybe the collective years of experience you all have can spot where I went wrong but I am currently satisfied with the conclusion that they were dead from the start (though I would much rather it have been something I did as that I can improve upon and learn from).
Going back to the beginning of this thread to see the pictures you posted, I agree that they were to say the least, very unhappy little campers when you received them. Not dead per se, but a good way there.
Some things I would have done differently:
- I never even use any chemicals on the roots. Especially peroxide is ver harsh on anything. I personally do not see the benefit, and it may well have done some harm
- I do not see any clay on the rootbals you showed in the pictures. So I think you have over-treated the roots. Next time, just put them in the ground and let them grow for a year. Then clean out the roots.
- Presing down on the soil between each handfullis only going to hurt the plants. You have such small plants here, there is no risk of air bubbels. The soil will compact sufficiently when watering. Air bubbels occur when you have larger roots, which prevent the soil from going all the way down. Think holes the size of ping-pong balls opr larger, not pebbel-size (I once thought my plant was potten properly. Started to work with a chiopstick and could put half a bucket of soil still in the container
In general: Less worry, and more let nature do its thing.