This seems a lovely idea, reminiscent of the cardboard grass chair which can be assembled and then planted with grass seeds so you can watch it grow. (treehugger.com)
You may cover the rocks with landscape fabric and place soil and / or grass seed on the top. (seattletinyhomes.com)
Then they plant annual rye or perennial rye grass seed to enjoy green grass all winter and into spring. (uglyhousephotos.com)