Flower bombs

A UK company has invented and are selling a fantastic idea: flower bombs.  They are clay hand grenades filled with flower seeds that you can launch into abandoned urban plots.  Interestingly enough the seeds in the bomb are three species often considered to be weeds (but not invasive): poppies (Papaver), buttercups (Ranunculus),  and ryegrass (Lolium).  All three will self-seed.