I don’t think the infrequent vibrations would contribute much to stem hardening. Granted, I’m not convinced the directly talking to plants thing contributes significantly to carbon monoxide harvesting. Just set up two USB powered fans that turn on and off every now and then. The gas you release as you sing My Humps from the kitchen will reach them.

Oh, no, this is the next big startup fad, isn’t it?

I thought the singing to plants thing was all about the directly breathing carbon dioxide onto them.

Obligatory “water is wet” post.