When you visit Hawai'i, if it rains a lot and it isn't the rainy season, you're most likely on the windward, or eastern, side of the island. Areas such as Hilo, on the Big Island, with 130 to 200 inches of rain per year and Mt. Waialeale on Kaua'i, the wettest place in the United States, with 460 inches of rain per year, feature the islands' most verdant rainforests. Although many of the state's native tropical rainforest plants are either extinct or listed as endangered, there are still several that you can see in their natural habitat.
The 'ohia (Metrosideros polymorpha) is a tree that figures more prominently in Hawa'ian mythology than any other plant in the islands. The tree itself is a bit of a gnarled-looking thing, with twisted branches. Then there is the lehua blossom, the tree's one redeeming feature. Usually fiery red in color, with the feathery texture of a bottlebrush, the lehua flower is a popular lei flower. The 'ohia is a slow-growing tree found in Hawai'i's tropical rainforests. Although it is the most common native tree in the state, it is currently fighting for its existence against non-native invasive trees, such as the tropical ash.
The koa tree (Acacia koa) is the second most common tree in Hawai'i, found in the rainforests on the islands of Hawai'i, Maui, Moloka'i, O'ahu, Kaua'i and Lana'i. Koa has historically been a valuable tree to the Hawai'ian people, used for outrigger canoes, weaponry, tiki gods and even birth control. Koa wood is commonly used today for souvenir items such as bowls, bracelets and picture frames. The koa tree is a large one, growing to heights of up to several hundred feet. It's also a heavy drinker, requiring up to 150 inches of water per year, depending upon its location.
Loulu (low-OO-lu) is a small palm tree, 10 to 26 feet tall, endemic to the island of Kaua'i. It is currently listed on both the State of Hawai'i and Federal Endangered Species lists, as there is only one remaining population--with four individual loulu (Pritchardia viscosa) trees--in existence in the wild. Sometimes called a fan palm, the loulu is a single-trunked palm with fan-like leaves. In fact, the loulu was used as a fan in ancient Hawai'i, its handle covered with coconut cord.