 Digging in swamps was more complicated ; a longer spear ( up to 8m ) was often used , often fitted with a hooked end to scoop out the lumps . Scrub was often cleared first with fire ; some got out of control and swamp fires could burn for weeks . Holes were often dug by teams in both hills and swamps — often up to 12m deep — and some wetlands were drained to aid in the excavation of gum . As field gum became scarce , " bush gum " was obtained by purposely cutting the bark of kauri trees and returning months later to retrieve the hardened resin . Due to the damage caused to the trees by the cutting the practice was banned in state forests in 1905 . Gum chips , small lumps useful for the manufacture of linoleum , were difficult to find , and by 1910 , the process of washing and sieving to retrieve the chips became common . The process was later mechanised . 
