My Favorite Gentian

The far Southeast of O’ahu is known for its surf. Whether it’s Hanauma Bay, Sandy’s, Makapu’u, there are plenty of places to get outside and enjoy the ocean-side of nature. But what of hillsides? Well, there is still a ghostly plant that makes its appearance from time to time when conditions are right. It is one of the few annual plants native to the islands. So join me on a quest for G: the Gentian, Schenkia sebaeoides that is.

As an annual, Schenkia (formerly Centaurium) sebaeoides has a very short life cycle. It sprouts after the winter rains, sets seeds, and dies all within a few months. This makes it more difficult to find the plant. You have to search the right places at the right time and hope that the conditions were right for germination over the winter.

We searched the dry hills over looking Hanauma Bay. The rocky slopes seemed like ideal habitat. While we weren’t finding any, we did come across another plant that is rare on O’ahu.

While not an annual, Pua Kala (Argemone glauca), does have a different life cycle. It is biennial, completing its life cycle in 2 years. This species is rare on O’ahu, found in mainly drier areas of the island.

We weren’t having much luck with the Schenkia, but we were coming across other rare plants.

Ma’oli’oli (Schidea globosa) is found in good numbers in the hills above Hanauma Bay. There aren’t as many weeds growing in this rocky area with full sun, and the Ma’oli’oli is the dominant plant in the area.

And since we were nearby, we checked out one of the strongholds for Marsilea villosa. This fern, which looks like a 4-leafed clover, is found in areas prone to periodic flooding. It is another plant that I enjoy seeing because even though O’ahu is so highly degraded, this island is the main population center for the fern. But enough of parochialism. The site, which 20 years ago had fields of Marsilea, only has pockets of the plant now. It hasn’t flooded in years and aggressive weeds have taken over. Although, hopefully the spores are still in the ground patiently waiting for the next rains.

We actually searched all day, finding no Schenkia. So, we gave ourselves a mulligan and went to one of the gulches that still has plenty.

They are small plants, less than 6 inches tall. Schenkia sebaeoides is the only member of the Gentian family that is native to Hawai’i. The seeds can stay dormant for a long time, creating a stable long term seed bank. They will germinate only when conditions are right. What this means is that populations can fluctuate greatly. A gulch that has thousands one year might only have a few plants the next and vice versa.

This part of O’ahu is so well known. Snorkeling, the Blow Hole, Burt Lancaster, these bring tourist to the area by the thousands. Yet, here amongst the bustle, this little Gentian survives. It certainly is a marvelous thing.


Schenkia sebaeoides 5-year review (pdf)

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