Spindly Apricots

No and No... they don't need support, they will develop a stronger root system without support... and leave them to grow and soon they will begin to branch. It's much too soon to think about pruning. You're growing trees, not shrubs.

Are they getting enough sun? Spindly often applied to plants that are not getting enough sun.

HB

I've been growing them in a greenhouse. It's been very warm this spring, and certainly not lacking sun. Having had great luck with Peach from seed, I assumed the same for Apricots.

Stone fruit trees don't do very well in a greenhouse, they become stunted. In order to properly develop these trees need to be exposed to the elements, to temperature fluctuations and wind - without movement the root system won't attain full form, without contraction/expansion from alternating temperature neither will the above ground portion develop a strong structure. And those are not saplings... get those seedlings outdoors.

Tree Stages

1. Seed
2. Seedling: the above-ground part of the embryo that sprouts from the seed
3. Sapling: After the seedling reaches 1 m tall, and until it reaches

1. Pole: young trees from 7?30 cm diameter
2. Mature tree: over 30 cm diameter, reproductive years begin
3. Old tree: dominate old growth forest; height growth slows greatly, with majority of productivity in seed production
4. Overmature: dieback and decay become common
5. Snag: standing dead wood
6. Log/debris: fallen dead wood