I have a solid tray on top of my heat mat. It keeps the water off the mat

I've often wondered about soil blocking, and how it might be advantageous to plant growth. With soil in cups, the roots are limited by the cup, and they just start to curve around when they reach the sides. With soil in blocks, the roots just fly through the sides, dry up, and die. Or else, if you cut the seedling bed into blocks, you're cutting off roots. So with soil blocks, you have to end up with fewer live roots, depending on how old the seedling is. Aside from not needing lots of containers, I'm not sure I see the advantage. Maybe I'm missing something, and someone can explain.

I have often wondered about soil blocking as well and never thought of the roots growing through the sides and dying. Thanks for the info Zen and Dan!

I use the little plastic shot glass cups, from the dollar store, and drill holes in the bottom to start my seeds. I can fit quite a few on my heat trays. I reuse them from year to year. (If it’s a bigger seed, like pumpkin, I’ll start in a bigger pot). This works well for me because I am sort of ‘frugal’ -lol- so don’t have to use much seed starting mix, which is expensive.

That's very true about the advantage not using lots of plastic. But when I grow seedlings in paper cups, I just recycle them, and when I grow in plastic cups or pots, I too just reuse them.

Thank you all for your input.

i usually seed in a system that I bought years ago and has worked pretty well overall. Due to covid, I have some time to experiment so am trying out coir pellets and soil blocking. and winter sowing. So far, I am not a fan of the coir pellets.. Seems to dry out too quickly. I just finished the soil blocking yesterday.so no opinion yet.

i appreciate your feedback and when I have results, I will report back!

I guess if the soil blocks are large, and the seedlings are small, little root damage would result. But keeping the soil blocks from crumbling requires, I guess, a careful recipe. Of course, as the seedlings get larger, the roots themselves will help hold the blocks together, but they will be more prone to damage. It will be interesting to hear about your observations in doing this.