Alan Moore is a legendary graphic novelist.

He penned “The Watchmen,” “The League of Extraordinary Gentleman,” “From Hell,” “V for Vendetta,” etc.

But Moore’s introduction to American audiences came in the early 1980s when he set an established DC Comics character on its boggy head.

He was tapped to write “The Saga of the Swamp Thing” monthly comic book.

Writer Len Wein and artist Bernie Wrightson created the Swamp Thing in the early 1970s. The concept: A scientist becomes a plant man after being consumed by flammable chemicals in a swamp.

What Moore did when he took over the title a decade later was change the character from being a man turned into a plant into a plant that wrongly believed it had once been a man.

With artists Stephen Bissette and John Totleben, and later others, Moore created a book of horrors that not only changed a character’s origin but delved into societal problems and a Brit’s look at America. He also introduced the character John Constantine during his “Swamp Thing” run.

In addition to Moore’s inventive plotting, he demonstrated a gifted way with words. For example: “It’s raining in Washington tonight. Plump, warm summer rain that covers the sidewalks with leopard spots. Downtown, elderly ladies carry their houseplants out to set them on the fire escapes, as if they were infirm relatives or boy kings.”

In a book where plants are ascendant that’s heady stuff.

Moore’s “Swamp Thing” run is collected in six trade paperbacks. Well worth finding. Well worth the price of admission.