PacSci Perspectives

In Awe Of The Awapuhi

by | Oct 10, 2016

A plant with a very unusual flower is currently blooming in our Tropical Butterfly house. Though it does not provide nectar to butterflies, the flower has a curious evolutionary history and a long tradition of human use.

If you go hiking in Hawaii, you may come across something close to the ground that looks like a greenish or reddish pinecone, surrounded by lush tropical shoots. This is probably not a pinecone, but instead the flower structure of a plant Hawaiians call “Awapuhi” or “Shampoo Ginger (Zingiber zerumbet). It’s closely related to the culinary ginger (Zingiber officinale) that you find in grocery stores. The flower structure (inflorescence) of the Awapuhi is made up of modified leaves called bracts, and many small pale flowers that emerge sequentially from the sides of the bracts.

Awapuhi Illustration

The Awapuhi’s claim to fame is the substance found within the bracts – if you squeeze the inflorescence, a wonderful, ginger-scented liquid pours out. Hawaiians traditionally used this fragrant liquid as shampoo, body wash, and conditioner. If you’ve ever perused the grocery store and seen a shampoo labeled as “Awapuhi,” this plant is the botanical inspiration for that product. (Although labeled as Awapuhi, many Awapuhi products don’t contain Zingiber zerumbet, but instead contain an extract from a related member of the Zingeberaceae family.)

This clear, gingery flower-liquid isn’t nectar – a sugary reward for some pollinator. It’s a plant substance called mucilage. Mucilage is a slippery, viscous substance with a complex molecular structure similar to plant gums or pectins. It’s found within most plants, and helps with plant life functions. Some plants have evolved to use it in specialized ways, such as for carnivorous plant insect traps.

Awapuhi Photo 02

Although people in Hawaii have used Awapuhi for centuries, it is not native to the Hawaiian Islands. It is one of the plants that Polynesians brought on their ocean voyages as they colonized the Pacific Islands from approximately 1400 BC to 12 AD. Their canoes were packed with useful plant and animal species that the Polynesians wanted to grow on their new island homes. It must have been challenging to keep plants alive on a long ocean voyage.  Awapuhi may have been chosen for its cleansing mucilage, but just as likely because it is a medicinal plant and a mild antiseptic. An organic compound, zerumbone, found in the Awapuhi plant is currently being studied for the treatment of cancer.

It’s difficult to say how the Awapuhi flower evolved, and why it produces so much mucilage – not much is known about its ecological origins before humans began propagating it two thousand years ago. Perhaps the mucilage served to protect the inflorescence from predators, trapping them like a carnivorous plant. Once humans started to enjoy Awapuhi’s shampoo-like qualities, they may have selected for even greater mucilage production.

Look for the Awapuhi plant when you visit our Tropical Butterfly House, but please don’t touch the flowers. This will help the flowers last as long as possible for all our guests.