GE Silicone II, clear exterior caulk should handle plastic without a problem.

As far as holding up out in the garden some plastics fade, get brittle, too light weight ect. If anchored down or shaded by a tree or patio it may look great for the summer. But it is just all depending on the calibur of plastic.

We will want to see this new and fun idea when you are finished. They do make plastic flowers and whirl-a-gigs.

About 5 years ago, I made an orange and yellow ($Tree stuff) plastic totem and it has been outside most of the time ever since! Only in for the hurricanes. It has held up well, and I like the orange and yellow! GEII!

I had alot of beautiful colored plastic bowls. My "test" for them was to try and scratch the finish off with my fingernail. Most of the color came right off , so I nixed those. As Susie said - the quality of the plastic might be the key.