[DigiDigiorno]

I'm surprised the seeds would survive the heat and pressure of a shotgun cartridge blast that contained enough gun powder to embed them in a wall

[bob1029]

Seeds are incredibly resilient in many cases. Also, shotgun shells come in a range of power level and configuration. Something like birdshot replaced with seeds would make sense to me.

[rigid]

it didn't embed them into the wall but in cracks and spaces where they could germinate.