JBP seedlings - full sun X dappled sun

I am growing a bunch of Black Pines from seed.
After the usual hot soak for 24hours and 3 month cold stratification in the fridge, they sprouted. It’s been seven months now.
Some of them were cut as soon as the stem turned to red, and the taproot was trashed.
The results are somewhat baffling, not expected at all.
The ones supposed to be the strongest are the smallest.
From left to right, the first one was left in dappled sun, protected from heavy summer rains. Its a future double trunk and it is the biggest of the three examples.
The middle one was left in full sun and full rain, and it is the smallest of the bunch, but the stem looks harder, woody. Same color as the first one.
The third one on the right side was cut (tap root) and left in the same conditions as the double trunk; the color is way lighter but it has needles all over, very low on the stem.
I can’t explain the reason for differences, does anyone could help?

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The first thought that comes to my mind is the fact that JBP love dry feet. This translates into practice when one ensures that they are allowed to dry out a bit before watering again, also in the practice of using very free draining media that is less water retentive than traditional bonsai mixes.
Perhaps in your climate the strength of the sun is considerable even in the shade and the rain is significant enough that the tree’s rarely dried out unless protected.
Just a possibility!

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Thanks, Frank.
Yes, rainwater can be the culprit. The ones protected from direct rain were only watered when dry; the others left in the rain were way wetter.
Summers here are usually very wet and it rains almost every afternoon, so…
Besides that we are having an unusual Autumn this year, as it is raining a lot when this was supposed to be the dry season. Now all of them are been kept in the same place and I will monitor them; if the conditions change, I’ll post the results here.

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Great photo, thanks for sharing! The seedling in the sun has short, but very straight, needles. It looks healthy to me. It’s not uncommon for trees in the shade to have longer foliage.

I like Frank’s idea that too much water may have slowed growth a bit, and the strength of the sun (high temperatures) can also stress trees. Plus there is variation among different seeds which can play a role.

Looking forward to seeing future progress!

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