Samuel Smithers was an assistant to a botanist who wanted to uncover the mental activity of plantlife. After a decade of research, the botanist died and Smithers took over his work. He wanted to try to find a way for humans to communicate with plantlife. With his work not taken seriously, Smithers was reduced to taking a job as a gardener. When a bolt of lightning struck Smithers' experimental device, he developed the ability to control and animate plant life. Seeking revenge against those who laughed at him and took his job away, Smithers became Plantman. On his revenge attempt, he was stopped by the Human Torch. He would later seek revenge against the Human Torch for putting him in prison, but failed once again. Smithers decided instead of revenge, his goal would be world domination, but he was foiled by Iron Man.
Mayor Story Arcs
Count Nefaria then broke Smithers out of prison to serve in his Maggia crime family. He and other lieutenants of Maggia ( Eel, Porcupine, Scarecrow, and Unicorn) fought the X-Men in an extortion attempt. Yet, the uncanny mutants stopped them in their tracks. After Samuel escaped prison again, he used stolen technology from Maggia and terrorized London. This was thwarted by Namor and Triton of the Inhumans.
Acts of Vengeance
Plantman would be one of many super-powered criminals that attack the Fantastic Four during the Acts of Vengeance. Plantman disguises himself in a trench coat and hat as members of the Fantastic Four testify in front of Congress. Plant Man and Quill remove their coats and head for the Fantastic Four but the two villains run into each other. Plantman's body is littered with quills while Quill is tangled up by a turbo charged vine. The two buffoons are handcuffed and taken into custody by the police. Mr. Fantastic would later discover that Dr. Doom was using an aggression enhancer device on the villains sent to destroy the Fantastic Four.
His constant experiments with plants paid-off when he succeeded in creating "Simuloids" which are plants given human form. He would often duplicate himself for mercenary missions. The Simuloids of himself have fought Captain America and the Falcon, the Defenders, Spider-Man, and even the Micronauts.
Blackheath eventually joined up with the Thunderbolts for some time before they disbanded. At this time, his plantlike powers had taken a new take and Samuel had become more plantlike. He then changed his name into Blackheath. He did not return to the Thunderbolts after the team reassembled again some months later.
In the Ultimate universe Samuel Smithers make his first apparition, in Ultimate Comics X-Men 19 "Reservation X", using the code name Blackheath. He's one of the twenty mutants who refused to take the cure, and is sent in Utah, in a land for mutants only. The land is highly intoxicated and Sam said he can't grew anything in this area, until Zero said he could cleanse it. Even if he agreeds to work with Shadowcat, Blackheath seems more interested in the plans of Mach Two and he's alleged to her