The native plant highlight for this Parker Press posting is the highly beloved and most dominant native tree in Hawai’i: ‘Ōhi’a Lehua.
Scientific Roots
‘Ōhi’a’s scientific name, Metrosideros polymorpha gets its scientific name from ‘Metrosideros’, which is a genus of trees, shrubs, and vines that are native to many places in the Pacific, and ‘polymorpha’, the Greek word for ‘many forms’ which refers to the fact that ‘Ōhi’a vary greatly, in their size, shape, flower color, leaf texture, the environment in which they grow; you get the point. ‘Ōhi’a’s ancestor likely landed as a seed from a Metrosideros species 3.9 million years ago, from Tahiti or the Marquesas. ‘Ōhi’a’s a wonderful example of adaptive radiation, as in that time, ‘Ōhi’a’s ancestor developed into five Metrosideros species and countless varieties, as it found the many biological niches that Hawai’i has.
(Left) A red lehua (‘Ōhi’a flower), called Lehua ‘apane, Kohala Mountains - Credit Kai Garcia-Tobar. (Right) Yellow Lehua - Lehua mamo, Kohala mountains - Credit Kai Garcia-Tobar.
Ecology
‘Ōhi’a is an immensely important species for the environment in Hawai’i. ‘Ōhi’a is known as a pioneer species since it is usually one of the first inhabitants of fresh lava flows. ‘Ōhi’a builds up the soil in these areas by breaking down rock and creating leaf litter, which allows other native plants to establish themselves. ‘Ōhi’a also serves key ecological roles in established forests. First, it harbors countless moss and fern species on its branches, which collect moisture from passing clouds and rain, effectively filtering it, and recharging Hawai’i’s aquifers. ‘Ōhi’a forests are a major cause of the quality of Hawai’i’s water.
Second, it provides food and habitat for Hawai’i’s endangered honeycreeper species. For the ‘Apapane, ‘I’iwi, and ‘Amakihi, it provides nectar in great abundance. For the ‘Akepa, ‘Elepaio, and 'Akiapōlā'au, it provides the insects and insect larvae that these birds survive on. For Hawai’i’s hundreds of endangered Kāhuli (native land snails) species, ‘Ōhi’a harbor fungus on its leaves, off of which Kāhuli feed.
A large ‘Ōhi’a tree, presumably hundreds of years old, Kohala Mountains - Credit Kai Garcia-Tobar.
Cultural Importance
Many oli reference ‘Ōhi’a, speaking on its importance to Pele and Laka, and inherent beauty, among other things. Ancient Hawaiians used ‘Ōhi’a’s exceptionally hard wood for poi boards, kapa beaters, weapons, idols, and the construction of canoes and houses. ‘Ōhi’a leaves and bark were and is still used for Lā’au lapa’au, traditional Hawaiian medicine.
(Left) Liko Lehua (Young ‘Ōhi’a leaf bud), Pu’u ‘o’o - Credit Kai Garcia-Tobar. (Right) Liko lehua, Kohala mountains - Credit Kai Garcia-Tobar.
Threats
Like many other native Hawaiian species, ‘Ōhi’a is threatened by development, deforestation, fire, and invasive plants and animals. But ‘Ōhi’a’s greatest threat is Rapid ‘Ōhi’a Death, or ROD. ROD is caused by two species of fungus called Ceratocystis. ROD is spread when fungus spores enter through wounds opened by wind, pruning, beetle boring, or feral pigs and goats. Trees often do not show symptoms for weeks to years after infection. But once symptoms start to show, large and/or entire parts of the tree’s canopy turn yellow and then brown in the span of a couple of days or weeks. The mortality rate of infected trees is 100%. Since its discovery in 2010, ROD has been spread to more than 178,000 acres of ‘Ōhi’a forest, and in some areas, 90% of the canopy has died back. ROD has been incredibly detrimental to the delicate ecosystem of native Hawaiian forests. Luckily, there are things that you can do to protect ‘Ōhi’a.
First, always spray and scrub your hiking gear before and after hiking. By spraying your gear with 70% rubbing alcohol and scrubbing with a clean brush, any spores on your gear will be killed.
Second, avoid moving ‘Ōhi’a plant parts from one place to another, as spores can survive on these and spread to new areas. This includes ‘Ōhi’a wood, flowers, stems, and leaves.
Third, avoid damaging ‘Ōhi’a trees. Remember that opening any wounds can potentially kill ‘Ōhi’a.
(Left) Lehua ‘apane, Pu’u ‘o’o - Credit Kai Garcia-Tobar. Liko lehua, Kohala mountains - Credit Kai Garcia-Tobar (Right)
‘Ōhi’a is a precious and exceptionally beautiful plant, which occurs only in Hawai’i. It’s our duty to do what we can to appreciate and protect this beloved tree.
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