Do you have any uses for the plant, or does it create interesting byproducts for you? Photosynthesis is not very efficient, but it is great at making complex organic molecules like sugar or cellulose.
But a plant needs more than power. It needs nutrients, usually in the form of fertilizer.
They also don't generally make hydrogen, not directly at least.
Another thing to consider: plants currently require a lot of natural gas or other fossil fuels to grow. Droughts and heat waves can disrupt production.