Among the first criminals the Atom (aka Ray Palmer of Earth-One) faced was Jason Woodrue, a horticulturalist with a knack for accelerating the growth of plant-life. An exile from another dimensional world of Floria, Woodrue sought to rule his adoptive world yet always faced defeat as the Plant-Master at the hands of the mighty mite. Twice it was during solo outings and a third time alongside fellow super-villains versus the Atom and his Justice League comrades. It turned out this third appearance of Woodrue was actually Doctor Destiny in disguise! Nevertheless, Woodrue would return an take his game to another level as he would years later become the receipient of his odd science.
In the parallel plane of Earth-Two, decades earlier another plant-themed felon attempted to use his gimmicked foliage in the form a haunted forest to extort money out of unsuspecting victims. Thanksfully, the rogue named Nightshade met his match and more in the form of Sandman and his partner Sandy. After a brief duel, it was thought that this crook met his demise amidst his own electronically controlled rubberized plants. However, he was mercifully extracted from this precarious situation and transformed by another villain from an alternate dimension into something more, but still as ugly as before!
As for Nightshade, he was rescued by sentient worm Mister Mind who used his alien technology to not only repair several damage to the criminal's body but also to transform him into a literal plant man as well! Not rechristened Ramulus, he joined Mind's Monster Society of Evil with a goal of eliminating the Justice Society of America (although those heroes were in an alternate cosmos, including Doctor Mid-Nite who ended up on plant world parallel to Floria). However, when faced with Superman and fellow All-Stars this modest assemblage of evil were unable to successfully claim victory. And thus ended the reported career of Ramulus/Nightshade, although he was left with his power to grow plant life and presumably his same inhuman appearence he had from the start of his career.