I'm growing several hundred seedlings in 2" soil blocks for the first time (no pots), and I thought I was being clever using felt as a capillary mat to water from the bottom.

The whole system is working wonderfully - the blocks are being watered properly, the seedlings all look healthy and are growing fast. However, I lifted one up yesterday and realized it, and all the rest, had grown straight though the block and woven itself into the felt!

The roots are much longer than I thought they'd be at this point and they're not ready for transplant (no true leaves yet). Every time I pick one up I rip a little piece of its root off.

Any advice? I'd like to not kill all these guys when I have to move them and transplant!