Rather than focusing on the dynamics of the actual lightning bolt, perhaps you could consider the mechanisms that occur before to discharge and breakdown of the air. Lighting forms from cloud to cloud, within clouds, and from cloud to ground, but also from ground to cloud.
The Feynman Lectures have some discussion of electric fields in the atmosphere. https://www.feynmanlectures.caltech.edu/II_09.html
and point out that we are walking around in a potential gradient most of the time anyway, so for your world you could look out how to have extremes of that. I think people have tried to come up with ways to capture the charge carried by rain drops, but it wasn't very successful.
In your case with the vegetation, as the previous posts mention, protective mechanisms to help discharge the actual strike might be more likely to evolve first, or might still be needed to protect the plant.
Anyway, the build up charge doesn't occur instantly, so perhaps there could be mechanisms that occur on biological time scale.
Electric eels have specialized cells each of which can have a voltage of about 100 millivolts, and then have several thousand of those cells stacked together to produce voltages of 800-1000 volts with substantial amperage that can discharge fairly quickly.
So perhaps there could be a similar like cellular structure where some form of rectification occurs when the charge build up is occurring, allowing a cellular battery like structure to charge up either chemically, or by polarizing a material. Or perhaps a super capacitor like structure could also be formed by the plant structure this would be a very high surface area organ within the plant where a conductive nanostructure is coated by an insulator. Although in our world on earth super capacitors tend to be low voltage devices. Or perhaps some genetic engineering is involved.
In writing this, I am mainly thinking of a non-earth like environment. However, even on earth trees can be viewed as electrical circuits and there are people who try to power electrical circuits from trees. (They don't produce much power)