Again, we tread on hollowed ground. There have certainly been more famous, better written, and more world changing comics than Alan Moore's Swamp Thing, but I don't think there has been any comic as hallowed. Swamp Thing is sacred ground, a comic that reduced most Top 10 lists to Top 9 before they ever get written.
So let's kick over the baptismal font, pants the wizard in his cave, and reboot Swamp Thing.
At his root (heh), Swamp Thing has a pretty basic premise: Plant Monster. While that might not seem like much, it was enough to spawn Swamp Thing's brother-by-another-mother, Man-Thing, a year earlier, the Heap decades before, and shambling mounds, the D&D monster, years later. Clearly, the idea of some sort of primal plantlife aping humanity has some draw.
So how much of it can we change? Moore has already beaten us to the punch with his reveal that Swamp Thing was not a man who became a plant, but a plant who thought it had been a man. Our Swamp Thing will still be Alec Holland, a living breathing human, but the shambling plant creature that is Swamp Thing will be no more than an animated shell.
Alec Holland lies dreaming in the depths of the swamps. He chose to lay there, to rest and dream, following the death of his wife at the hands of her uncle's mad quest for immortality. Anton Arcane had trapped the previous Swamp Thing, using the creature's connection to The Green to attempt to upload his own consciousness to the world and thus live forever. When Abagail found out that the heap of plant matter she and her husband had been studying in the lab was actually a living, thinking being, she attempted to free it. Arcane stopped her with lethal force. Seeing his wife's passion through, Alec granted the vivisected Swamp Thing it's wish to die, ending it, severing any chance Arcane had of using it as a vessel to immortality.
Once a human touches The Green, though, it changes them. The Green simply does not let go. Alec's dreams began to change. He dreamed of his dead wife, which were understandable, but she told him things that were not. Abagail Arcane is part of The Green now and Alec can go to her in his sleep. The Green's touch, or rather its firm backhand, also affected Arcane - he can no longer consume plant matter without it making him violently ill, spores and pollen provoke allergic reactions to the Nth degree, and even touching a simple leaf causes him to break out in hives.
Lead on by the plant-ghost of his dead wife, Alec takes on the mantle of Swamp Thing. Not wishing to subject its new champion to the same fate as its previous, The Green does not change Alec into a shambling mound. Instead, it grants him the ability to shape his own mossy golem from plant matter while he sleeps. Swamp Thing can appear almost anywhere there is sufficient plant life, controlled remotely by a dreaming Alec Holland (the implications of this and of Alec's growing dependance on plant-based sleeping aids that allow him to "stay under" longer will be explored in the series). Alec is an agent of The Green now, its knight in shining tuber. Guided by the ghost of his dead wife (is she real? a hallucination?) Alec works to defend The Green from its greatest threats, Anton Arcane (who has found a way to disrupt the harmony of The Green) and The Red.
Yes, that's the same Red that gives heroes Animal Man and Vixen their powers. Remember that The Red and The Green are rivals and it's that conflict that drives each to improve themselves. Think of them like England and France in the middle ages. Sure, they'll team up against an external threat (the Ottomans, say, to torture the example), but most of the time they're at each others' throats. Consider that The Green has other agents, ones that are widely regarded as villains like Poison Ivy and The Floronic Man. So what happens if Vixen tries to stop Poison Ivy from, say, turning a populated city block of Gotham into a new rainforest? Swamp Thing could easily be called in to assist the villainess. Alec will have to walk a fine line with his duties to The Green on one side and his basic humanity on the other.
Still, for the first story of Swamp Thing (#46/52), we'll keep the focus on Arcane, who due to The Green's curse, has had to turn to other options to achieve his goal of living forever. Weirder options.