Harry Wheatcroft’s Rose

Origins
Wheatcroft was an English planter who grew roses, bolstering its popularity among British gardeners. He and his brother Alfred created their own gardening company, specializing in roses. He split from his brother and went into a rival company with his sons, buying out Wheatcroft’s old business. He gave them control of the daily operations, while he handled his public image.

Effects
When a person pricks their finger on it, it releases a virus which rewrites their DNA turning them into a homicidal plant-human hybrid that will protect the rose at all costs and kill people to feed the rose with it's blood. All affected die in 48 hours, though destroying the flower negated the effect.