I have a little area that I keep turned over for planting every summer. I gave planting seeds in egg shells a go during the winter and had a little luck with green beans and squash. I just planted the whole thing shell and all giving the plant and ground more nutrients.
I feel like your garden is only as good as your dirt is. I always start with good garden soil and turn it along with the earth.
Pot planting is excellent when you don't wanna mess with a bunch of plants. You can still yield a lot if you keep them watered and "dead headed."
I usually use the egg carton to start my seeds, i never thought to use the egg shell itself...
Is your garden organic?
It's too late for me now because of the soil I used but I want my "real" garden to be organic.