Opinions needed for JM seedlings

[sfeagan]

This is the first time I've got JM seeds to sprout. I know I put too many in such a small tray but I really didn't expect that many to sprout. My question is... How long should I leave them in the current trays and should I continue putting the humidity lid on? I know I'm going to have to separate them sometime but I don't want to do it too early. I'm really worried I'm gonna leave them in too long or take the lid off to early or vise versa. They are currently in my workshop where I have heat pads and a UV light. I don't think I need the heating pads anymore unless it helps them to stay strong. Any advice is appreciated!!

 

[Wulfskaar]

That looks a lot like my workbench lately.

I am also curious about this since I just lost my jacarandas and dawn redwoods. They were too leggy (not enough light) and I put them outside too fast. I left no in-between period to properly harden off. My sweet gums did just fine.

I just read that once the seedlings have broken the soil surface, it's time to stop using heat and humidity. I don't know how true this is or if it's species-specific. I kept heat/humidity going until they were about the size of yours. I think I just put them out in the sun too fast, then the air got very dry. The change was too abrupt.

I'm looking at starting round 2 soon, so I'll be following this thread for pointers.

 

[Hack Yeah!]

I'm not an expert but rooted seeds should only need soil moisture... bottom heat should be fine. Remember to acclimate them slowly to sunlight

 

[leatherback]

For next time.. I personally consider it a mistake to start them in a heated space. As bonsai you want compact trees. Anything that increases the light-to-heat balance will induce short compact stems with close internodes. The more heat you add the lankier the growth will become.

That being said.. Separate in individual pots or better spaced trays after the first real leaves have grown out and the central stem starts growing. At that point the seedling is less brittle and has formed the basic internal structures, taking handling much better. Make sure to clip the main root at that time too, even just a fraction of an inch off does wonders in ramification of the roots.

 

[Shibui]

Seedlings can be transplanted any time from germination right through to many years old. The recommendation of 'first true leaves' is really just to make them easier to handle. Definitely trim roots when first transplanting. That is the best time to start on good nebari. Young seedlings have the ability to recover from really harsh root pruning so you do not need to be gentle with roots at this stage.

Leaving them crowded can cause problems. Crowded seedlings restrict air movement and can promote fungal growth. If damping off gets started it can move very quickly through overcrowded trays.
+1 for starting seeds outside in natural sunlight. Appears to be much better odds and better results here.
Usually seedlings that are transplanted into individual pots grow way better than those left in community trays. Roots have more room and less competition for space, water and nutrients but I have also left seedlings in trays for several years - slow growth but they survived OK. Once got hold of a tray of red pines seedlings that were 10 years old and never transplanted. Still very skinny but they survived and did well after transplant. I still have a couple.