|Ohi'a Lehua (Metrosideros polymorpha) clinging to a crack in a 1974 lava flow on Kilauea|
|Ohi'a Lehua (Metrosideros polymorpha). The trees are threatened by Rapid Ohia Death disease.|
The Ohi'a is one of the most remarkable tree species on the planet. The Latin name polymorpha ('many shapes') provides a clue why: it can grow in a stunning number of deeply contrasting environments. Ohi'a trees can be found as the first pioneering species on fresh lava flows, as in the pictures above. They can be found on the near-desert leeward slopes of the island's volcanoes. They form the canopy of most of the island's rainforests, growing to heights approaching 100 feet (30 meters). They grow in near alpine conditions at 8,000-9,000 feet on Mauna Loa and Mauna Kea. And stunted trees, barely shrubs, survive in the high altitude bogs on Kauai where the rainfall exceeds 300 inches a year. I know of no other tree species that is capable of such feats.
It's true that you could try and cultivate Ohi'a trees in these kinds of environments elsewhere in the world and they might not do very well in competition with other established species. On Hawai'i, though, all they have to do is survive, because the isolation of the islands has meant that only a handful of other tree species ever arrived. So it is that in the unending battle between rock and life in Hawai'i, the Ohi'a tree is often the main combatant.
The Ohi'a trees aren't entirely alone as colonizers of barren landscapes in Hawai'i. The ʻŌhelo ʻai (Vaccinium reticulatum) is a shrub that can be found on new cinder cones, ash fields, lava flows and alpine slopes. The berry is edible, and is a treat for the nēnē, the native Hawaiian Goose. The geese in fact have a lot to do with spreading the seeds in the inhospitable environments of volcanic landscapes (they leave the seeds in their droppings). I'm trying to think of any other plant or shrub that produces mature fruit when it is only an inch or two high (as in the picture below).
|ʻŌhelo ʻai (Vaccinium reticulatum)|
|Life creeps ever higher towards the barren summit of Mauna Kea|