Cyanea tritomantha are towering giants among the remaining cyanea of Hawai'i. After a decade or more of slow growth in the rich mud and moss of Hawai'i's rainforests they finally become tall palm-form adults, with trunks up to 3 inches diameter and a broad crown of leaves each up to three feet long. As adults they can finally begin to flower and fruit, with tight clusters of large flowers among their leaf crowns. I'm uncertain how many years the adult plants can flower, but I've seen a high fraction of the flowering adults I know of die in the span of just 3 years. I frequently visit a few scattered remnant populations along Stainback Highway. They are widely distributed in the island's wet forests and have not yet become endangered, but mortality is high and without protective fencing this slow-growing species would continue to decline.

They are similar in stature and appearance to cyanea macrostegia on Maui.