1. It will work. Probably will stink a bit.

2. The leaves from a non-blooming plant will root. The leaves from a blooming plant will root too.

I would say that this lady developed some methods that worked for her - she probably used dirt from the garden and didn't have access to modern fertilizers with microlelements - so her approach was good in her conditions and didn't do any harm. With more intense methods - when we keep the plants under the lights, use wicks, soilless mix, constant fertilizing - they bloom all the time - so waiting for them to stop blooming and use egg shells for the fertilizer that comes from the residual organic matter on the insides of the shells seems a bit too much.

I.

Don't know if it would work but that must have look very cute like a little sail boat. :)

That's very interesting. I haven't heard of that, but I have heard of putting eggshells in the water you use for them.

The calcium from the shell supposedly leaches into the water.
Some growers use eggshell in their soil mixes.

Linda