RuneScape Classic Wiki
The main RuneScape Wiki has an article on: Dwellberries
The Old School RuneScape Wiki also has an article on Dwellberries.

Dwellberries are needed to make a gasmask used in the Plague City quest. They can be found in McGrubor's Wood near the guard dogs, or sold by Heckel Funch and Hudo glenfad within the Grand Tree. They are used in Gnome cooking and they heal 1 Hits when eaten.

Item spawns

Location Number of spawns Number in stack
Found on the east and west side of McGrubor's Wood (2 each side), beware the guard dogs 4 1