Daniel Palmer, in “Hawaii’s Ferns and Fern Allies,” calls Hypolepis “a poorly understood tropical and temperate genus…represented in Hawaii by a single endemic species…” That single endemic species is Hypolepis hawaiiensis, with the Hawaiian name olua. Olua is found in wet montane forests on all the islands. On the Big Island, olua can be easily overlooked when small as just a bracken fern, but as it matures, it grows very large and distinctive.
Olua may be found by the side of the Halema’uma’u Trail in the National Park. From the crater floor, walk up about 5-10 minutes and look on your left for a large mamaki tree (worth a visit in itself). Nearby is olua. It grows straight out of the ground with fronds extending over your head, so be sure to look up. If you look down, you will see the emerging fiddleheads, which are a very bright green and sticky and hairy. Very strange. In fact, the older fronds are also sticky and hairy. I’m told the olua on Oahu do not have this unusual characteristic. Also, they are not so gigantic there. And, just to add to the confusion, Maui has a rare miniature variety, with mature fronds as small as 2 1/2 inches.
This is perplexing, but well within the nature of ferns, which are so hard to identify, especially for non-botanists. Nonetheless, this lone Hawaiian representative of a poorly understood genus is well-worth a visit.
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