Short answer: yes, in principle—but I would not treat every urban trash can as a ready-made planter. A lot depends on the bin’s design, who owns it, and whether it still needs to function as a trash can. If you mean putting pots or a shallow planting tray on top of a public bin, that can be a quick greening idea, but only if the top is stable, the bin can still be opened and emptied, and the setup does not create a hygiene or safety problem.
The biggest practical issue is drainage. Plants need holes for excess water to escape. If water sits on a metal lid or in a sealed container, you get root rot, rust, mosquitoes, and slippery surfaces. A better approach is to use a separate planter tray with drainage holes and a saucer, or a purpose-built bin planter with a reservoir. Also think about weight: wet soil is heavy. A large container on a curved or hinged lid can bend the lid, block access, or make the bin unstable. Keep the planting shallow and lightweight, and check the load limit.
Then there is hygiene. Trash cans attract pests, and plants can make it harder to clean the lid or open the bin. Avoid planting edible crops on or beside a public trash can. Choose tough, low-maintenance ornamentals, and keep soil covered to reduce litter and smells. If the bin is used daily by the public, maintenance has to be realistic: someone must water, prune, remove trash, and check for damage. In hot, dry cities, watering may be the hardest part.
Materials matter, too. Some metals rust, some plastics become brittle in UV light, and painted surfaces may leach or flake. Use liners or separate pots so soil and water do not sit directly against the bin. Check local rules before modifying public property; many cities require permits or prefer that residents adopt a nearby tree pit or use dedicated planters instead. A removable top planter is usually safer than drilling into a public bin.
So, can urban trash cans be used as planters on top? Yes—carefully, and mainly as temporary or decorative add-ons. If you want a long-term solution, dedicated planters, integrated bin-and-planter units, or small green roofs designed for street furniture are better choices. The idea is promising, but safety, drainage, access, and maintenance decide whether it works.