I saw this in a magazine and we are trying it.
These are half eggshells with a hole poked in the bottom and a seed in each one, with dirt. Once they sprout, we will be able to plant the whole half-shell into the veggie boxes and they will compost. Ideally, the shell will compost in the veggie box before the veggie needs the space (I wonder how long it takes eggshells to break down).
This is appealing because:
1. We have a lot of eggshells
2. The chickens are quite loved and discussed around here
3. Same for gardening
4. The little baby veggie roots may have a better chance for survival if we don't disturb them when transplanting