Harakeke was used for Rongoa (medicine). Roots were roasted on hot stones, and macerated into a poultice for abscesses and ulcers. They were also boiled and used as a blood purifier. Flax root juice was applied to wounds as a disinfectant. The gum at the base of the plant was used for treating burns and ringworm. Toothache was treated with a few drops of juice from root or leaf base in the cavity of the affected tooth or in the inner ear. Splints for broken bones were made from leaf bases, and flax fibres or strips used for sewing up a wound.

The flower nectar provided a beverage and food sweetener while flower stalks were tied into bundles to make rafts. Seed pods were used to dye fabric.

Its importance has not diminished over time, and today certain protocols must be followed prior to harvesting the plant.