In article ,
Roger Whitehead wrote:
A gardener I know reckons that rain falling during a thunderstorm will
carry an electrical charge that's especially beneficial to the plants it
falls on, even waking them from a kind of dormancy.

Sounds like rubbish to me but I'm no scientist. Are there any facts for or
against the notion?

I'm not a scientist either, and it sounds like rubbish to me, too, FWIW.

However, it may be a garbled remnant of the true situation -- lightning
discharges produce nitrogen oxides which are a significant natural
source of nitrates when they are washed out of the atmosphere by rain.
I've seen calculations of the annual amounts for agricultural areas and
they are not insignificant -- i.e. not enough for corn, but plenty for
forest and grassland. It's one of the ways the nitrogen cycle is closed.