Jam Jar Greenhouse Project

I am building a Greenhouse out of old jam jars (actually I am using any glass containers - does not have to be jam). And I thought it would be cool if I could use some of the jars to collect rain to water the plants inside the Greenhouse. This is my first 3D printed prototype, I have tested the concept with a metal lid, it works fine but it has a deadly sharp edge and its ugly (see photo).
The greenhouse is built out of glass jars with the open end facing inwards. The rain collector jars have