Can you make a large flower pot using a large trash can?

If you know what growing conditions of the plant, and how much soil they need...it’s possible. You will need a hole in the trash can so the roots won’t drown.

yes just put some small holes so water can drain out of bottom make them lrg enuf they don't get plugged easily but small enuf you don't loose your soil 16 penny nail size works well if it's metal you may want to line it with plastic trash bag so it doesn't rust

Of course - what a creative idea! Make sure you drill some drainage holes in the bottom first. If it's a tall can and you don't really need all the soil it will hold for the depth of the roots, you can fill in the bottom with empty milk jugs. Just remember though that this might make it top heavy, so it really depends on how large your can is and how much soil you put in. You could also really get creative with decorating the outside of your planter. Here's a couple of ways I've decorated traditional planters that you could adapt. Best wishes on your project - you're so creative, Jo!

https://www.toworkwithmyhands.com/2018/07/how-to-make-a-super-quick-and-easy-cute-planter.html

https://www.toworkwithmyhands.com/2019/04/faux-galvanized-flower-bucket.html

Also, if appropriate, plan ahead on how you are going to move that heavy load in the fall. I once made the mistake of copying an idea to lighten the load by using Styrofoam peanuts in the bottom of large pots. Made the pots lighter, but what a mess when I dug my cannas out of the pot and what a mess cleaning up the peanuts when I wanted to re-pot plants. Solution. Get a dolly to move your huge new planter.

You sure could. You'd just need to drill drainage holes in the bottom.

how large .. it may need to be submerged ..lol