I saw some designs of planters here on Thingiverse, also those with a water-reservoir and a jar on top as a small greenhouse, after that i also saw a few to put into a jar, but they only where resting loose on the jar, i wanted one which could be scewed onto the jar. So i designed this as my first project in Fusion 360, hope you like it.

I designed it to fit into jars of a brand called 'Bonne Maman'. I plan to make more models to fit different sizes and shapes of jars and also for different planting needs (smaller space for plant, so that the roots dont spread too fast etc).

To better use the reseroir you could put thick strings through the holes at the bottom, so they suck up the water from farther below.