Pomaderris kumeraho or kūmarahou, also known as gumdigger's soap, is a plant endemic to the North Island of New Zealand. The name kūmarahou is a Māori word signifying a shrub.Kūmarahou grows up to four meters in height, and flowers in September, with yellow blossoms. The name "Gumdigger's soap" was given owing to the lather created when the flowers were rubbed with water.
Kumarohou is a plant of poor soils and is found from North Cape to Kawhia and the Bay of Plenty. Kumarahou makes lather if the leaves and flowers are crushed and stirred in a bowl of water. This lather is functional for bathing and washing clothes. The leaves were also used as an infusion and are claimed to have medicinal qualities, used for treating such ailments as coughs, bronchitis, asthma and heart burn. It had a reputation as a treatment for tuberculosis.
Kūmarahou has many uses in traditional Māori medicine, although there is little scientific confirmation of its benefits.Infusions of the leaves have been said to relieve various respiratory ailments and skin disorders.