A little experiment with green prints and concrete.
I proceeded very carefully to fill the molds up with concrete, making sure not to damage the prints.
I used watercress seeds. I also wanted to make sure the prints would grow green as soon as possible so I decided not to mix seeds into the soil mixture but to apply them later on top.
Watercress sprouts very quickly. This is the result after about six days.
Watercress also withers away very quickly. So after that I washed the withered plants and soil out of the concrete blocks and filled the holes up with fresh soil and grass seeds. The grass stayed green for about two months.