Here is another fern we have at the Manoa Cliff restoration site. ‘Okupukupu (Doodia kunthiana) is another endemic component to mesic-wet forest understories here in Hawai’i. It may be common in other areas, but I have not come across this species often on my hikes.
Having a 1-pinnate frond, D. kunthiana can easily by confused with the more common native swordfern (Nephrolepis exaltata var. hawaiiensis) Indeed, both species share common names in Hawaiian; ‘okupukupu, pamoho. (side note: ni’ani’au seems to be reserved only for Nephrolepis) But there are some ways to distinguish between the two.
Here are two fertile fronds of different ‘okupukupu: Nephrolepis exaltata on the left, Doodia kunthiana on the right. You can see that near the top of the Doodia frond it is actually pinnatifid. There is also a noticeable grove on the rachis of Doodia though I’m not sure if this is diagnostic for the species. I also don’t know if the difference in the color of the frond is a reliable indicator.
Taking a look at the abaxial surfaces you can see that the sori are much different. On N. exaltata they are kidney shaped while on D. kunthiana they more medial on the pinna and parallel to the costa.
Another thing to look at is the color of the new fronds. Like it’s native blechnaceae relative Sadleria, the new unfurling fronds on Doodia are a reddish color. You can see that in the photo at the top.
Anyway, this is a quick post on another member of our native Hawaiian flora. So next time you come across a strange looking kupukupu in the forest, take a closer look. It might be a different member of our native plant community from what you might be expecting.