Piper excelsum (formerly known as Macropiper excelsum), called Kawakawa, is a small tree of which the subspecies M. excelsum subsp. excelsum is endemic to New Zealand; the subspecies M. e. subsp. psittacorum is found on Lord Howe Island, Norfolk Island and the Kermadec Islands
It is found throughout the North Island, and as far south as Okarito (43.20 °S) on the West Coast and Banks Peninsula (43.5 °S) on the east coast of the South Island. The leaves are often covered with insect holes. The images depict the variety majus which has larger and more glossy leaves than M. excelsum. The name Kawakawa in Māori refers to the bitter taste of the leaves, from kawa bitter.
The Kawakawa leaves are about 5–10 cm long by 6–12 cm wide; they are opposite to each other, broadly rounded with a short drawn-out tip and are heart-shaped at their bases. The leaves are deep green in color if growing in the forest but may be yellowish-green when growing in more open situations.
The flowers are produced on greenish, erect spikes that are 2.5-7.5 cm long. Kawakawa flowers are quite minute and very closely placed around the spike. After pollination the flowers gradually swell and become fleshy to form small, berry-like fruits that are yellow to bright orange.
Each berry is the size of a small plum and egg-shaped. Ripening period is January and February. These fruits are favoured by kereru, or New Zealand pigeon (Hemiphaga novaeseelandiae) and tui (Prosthemadera novaeseelandiae).
The leaves of kawakawa are used to make Kawakawa ointment, which is a natural anti-bacterial and anti-inflammatory.  Titoki Liqueur, which is exported to Japan, Australia, Fiji and the United Kingdom. The seeds of this plant are employed as a culinary spice and they could be commercially used for that purpose, as this tree is related to Piper nigrum (black pepper) and it is grown as an ornamental plant.
Kawakawa is a traditional medicinal plant of the Māori. An infusion is made from the leaves or roots, and used for bladder problems, boils, bruises, to relieve pain or toothache, or as a general tonic. The sweet edible yellow berries (most often found in summer on female trees) of the plant were eaten as a diuretic. Host people of a marae wave leaves of kawakawa to welcome guests, especially at tangi. Both they and the guests may wear wreaths of kawakawa on the head as a sign of mourning.
- It has also been surmised that when Māori first came to New Zealand, they named the plant 'Kawakawa' because they recognised that the plant was a close relative of Piper methysticum, the plant from which kava is made in the tropical Pacific. However, given that Piper species also occur in tropical Polynesia, it is more likely they simply applied the name of those plants to the New Zealand variety. In the Cook Islands and the Marquesas for instance, M.latifolium is known as 'Kavakava-atua'; in Samoa it is called 'Ava'ava-aitu'. M. latifolium is very similar in appearance to the New Zealand species, and is also used in traditional medicine in the Cook Islands.
- Bone, K. "A clinical guide to blending liquid herbs". St. Louis, MO, Churchill Livingstone, 2003.
- Brooker S.G., R.C. Cambie & R.C. Cooper, New Zealand Medicinal Plants. Heinemann, Auckland, 1981.
- Metcalf, L. "Know your New Zealand Plants". New Holland Publishers (NZ) Ltd, Auckland, 2009.
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