" ... be careful of the Venemous Tentacula, it's
-- Professor Sprout in Greenhouse Three (CS6)
A spiky magical plant with teeth.
- The vines of this scary plant reach out toward people when it is teething (CS6).
- The twins bought seeds of this plant from Mundungus Fletcher for use in their Wheezes (OP9).
- A wizard named Derwent Shrimpling became famous for Eating a Venomous Tentacula, but his skin remains purple to this day (FW, JKR).
- The bite of the Venomous Tentacula can be fatal. Minerva McGonagall's husband Elphinstone Urquart died of such a bite three years after they were married (Pm).
- One of the plants used by Professor Sprout against the Death Eaters during the Battle of Hogwarts (DH30)
"tentacula" probably refers to the reaching tentacles of the plant