Sounds like a fun mess and a great way to keep the city green. Banknotes are paper, so you’d need a biodegradable matrix to hold the soil and seed. I could mix some compostable polymer with the old bills and test a tiny planter. The glue will have to be plant‑friendly too, or it’ll just decompose without holding anything. Let’s prototype a few and see how the notes behave in the soil—if it works, we’ll have a quirky little garden mosaic right under the traffic lights.