I would think the flex in the container material would cause anything applied to separate very quickly. I'd start with spray paint.

Depending on the type of plastic, the concrete, mortar or stucco may not stick at all. And it is much harder to get it to adhere to a rounded surface than it is to a flat one.

I'd experiment with sanding or scruffing the sides of the plastic pot first, then apply a thinnish layer and see how well it sets and attaches.

I would also try something like paper mache, which can be successfully waterproofed for outdoor use. Your creativity with this has few boundaries !! 😊

The above posters are correct, it has difficulty sticking. For papier-mache, use outdoor waterproof glue and outdoor paint to coat it.

Rustoleum, Krylon, and several other major brands make lovely pebbled spray paint in several colors that has a nice grainy texture that might please you. It's reminiscent of a concrete, although the colors aren't as pebbled and variant (you could touch that up with dots of outdoor acrylic paint if you want). Still, from a short distance, it'll do. Most big box stores carry this.

This is certainly the easiest method. :-)

For the very, very exacting (me), rough the surface with sand paper and apply a mix of either 2 part craft epoxy and mixed color sand or UV craft epoxy and 2 color sand (what, doesn't everybody have all this on-hand?) :-) Fix to surface with time or UV light. Sandpaper to remove any bumps or lumps. Bingo, sand-surface pot.

Given the rounded surface, I'd probably use the UV resin here, but since the sand thickens it, you could probably do a third of the pot per day even with regular resin and you wouldn't need much.

Thanks @morpheuspa I think I will do the sand/epoxy coat and then spray paint.

I used the Rustoleum paint and the texture in the paint constantly clogged in the sprayer, created a mess of coverage and had to buy twice as much to cover the planters (I’ve been confined to container gardening for awhile now...), though maybe I just got a bad nozzle.

I wonder if I could use strips of burlap in slightly runny concrete and do a paper mache over the pots that way? They’re 24” h x 24” diameter and have a wicker/woven-looking texture in the plastic.

As you can maybe tell, winter + covid measures have me a little bored and restless 🙂 and this is where my mind wanders...

this sounds messy 🙂 I like it! Thanks for the ideas, I will post pictures if it turns into something worthy.

(And sounds like I better buy some gifts from you... closer to next Christmas!)

Look into "draped hypertufa" eg: https://www.thehypertufagardener.com/oh-the-possibilities-draped-hypertufa/

Probably will give you some ideas on how to use cement in your projects. Here are other search terms that may be useful for you: hypertufa, papercrete, shapecrete

Shapecrete if off the market but there are recipes out there to sort of replicate it. But it was a wonderful product. It allowed some flexing. You can achive some of that flexing ability by adding "flexbond" thinset used for setting tiles. Still it will not bond to plastic but allows some slippage.

You can also borrow some ideas from a product called "bondo" used to fix dents in cars. It uses a combination of mesh (for strength) and fillers/glues similar to epoxy.

Drywall mesh tape is also handy material. It will initially stick to plastic. Then using a soldering iron you can hot melt at spots to permanently tack it on to plastic pot. Needs a bit of practice - start with a medium setting on the soldering iron if you go this route. Now you use that surface to apply your next layer of epoxy, cement whatever. Go in thin layers and build it up. It will hold longer. You can even mix in colors and or stain later to give it more natural rock like look.

Besides sand, you can use sifted fine perlite, peat or other fine particles or a combination of these. Expands the possibilities of texture and strength. Sand will be the strongest. Perlite will produce the lightest mixture. But you can increase the strength and sticking power by adding concrete fortifier (available in those bog box stores).

And wear mask when handling dry cementitious products. Not good for your lungs at all.