Gum Tree Berries are large berries from the Gum Tree Zone that are grown on trees. The bulbous blue fruits may or may not be edible to the general populous, but the juice inside them are corrosive to metal. Amy Rose somehow knew this before the Freedom Fighters intercepted a transport in the Zone. During a tough fight with new weapon Vermin the Cybernik, Amy used her crossbow to pierce one of the berries. The "acid" inside dripped onto Vermin, causing his armour to dissolve. The Cybernik fled the battle, with nature proving to be the winner. This encounter suggests that the berries are one of the only things capable of destroying Megatal.
These berries were later utilised by Knuckles the Echidna during the Floating Island's attack on Doctor Robotnik and his aerial troops. Tikal piloted the landmass over the Badnik invaders and Espio the Chameleon fired the corrosive juices. While the native Gum Tree Zone berries were seen to be a deep blue, the acid unleashed from the island was a vivid green.
The fruits were originally named Gum Tree Sacs or Gum Tree Fruit. As of Issue 250, the name of the fruit has been changed to the current one.