Koko Crater Botanical Garden of Honolulu

Koko Crater

Koko crater is one of at least 5 major volcanic craters on the Hawaiian island of Oahu. Koko is perhaps the youngest of them, having started to form 40,000 years ago, intermittently erupting until 7000 years ago. And, it may not be done yet. Two of the other more famous craters on Oahu are Diamond Head and Punch Bowl craters.

Looking east from downtown Honolulu one sees the profile of Diamond Head crater. Just beyond Diamond Head lies Koko Crater, rising to a height of 1000 feet. It is an easy 20 minute bus ride from Diamond Head, and 30 minutes from Waikiki beach.

The 60 acres of the Koko Crater Botanical Garden is situated in the bowl of the crater. The conditions there are desert-like due to the absence of either rainfall or run-off from the larger nearby mountains on Oahu. The Koko Garden is one of the five botanical gardens owned and operated by the County of Oahu's Honolulu Botanical Gardens. Entry is free of charge, but services are minimal and limited to a few picnic tables and a porta potty. If you go, bring your own water.

As with other botanical gardens on the Island, the grounds are arranged in sections according the area of the world where the plants originated.

Hawaiian plants in Koko Crater Garden

There are several native Hawaiian plants on display in this garden. The arid biome isn't typical of most of the Hawaiian landscapes, consequently there are relatively few endemic desert-adapted plants in Hawaii. But, the Koko Crater garden has a few notable examples of Hawaiian plants that tolerate the dry conditions.

Distinctive sickle-shaped leaves of the koa tree

Koa wood reminds me so much of mahogany with its deep reddish brown color and tight wood grain. The Latin name for the tree is Acacia koa, it is in the bean family of plants. The tree is native to Hawaii and once covered the hills and mountains at higher elevations. The trees were a source of income for the noble ali'i after Western contact in the 1800's, which caused the native forests to be severely defoliated, along with the harvest of native sandalwood trees (Santalum haleakalae). 

The dark brown hardwood of koa is very popular for making furniture, bowls, tools, and canoes. The examples of koa trees in the Koko garden are all relatively small, allowing one to get up close and personal with the leaves. Out in the forests, the trees are usually taller than 50 feet tall and the leaves are either way up in the canopy or dead and brown on the ground.

Pritchardia palms (Loulu in Hawaiian)

Pritchardia palms (Loulu in Hawaiian) is the only palm trees native to Hawaii. Coconut and other palms were introduced by early Hawaiian settlers over 1000 years ago and have become naturalized. There are 24 species of the loulu palm found across the Islands. Each island has at least one species unique to it, most vary either in height or the shape of their flowers. The palms are endangered in Hawaii due to habitat loss, rats, weed, and feral animals. Early Hawaiians used the plant for thatching and weaving cloth. 

Wili-wili tree

This small species of Erythina sandwicensis (wili-wili in Hawaiian) is endemic to the low-land areas of Hawaii. Of all the native trees this one has the lightest weight wood. It was used for outrigger canoes and floatation buoys on fishing nets. The seed pods are flat like a snow pea, but twisted in the middle giving the pod and curly shape. Inside the pods, the seed flesh is bright orange, and the inner seed pits are hard and black. When polished the smooth seeds make attractive leis. The Hawaiian word for twisted is wili-wili.

The flowers of this tree are orange, and it is said the tree bark has a distinctive orange algae. The bark also sports 1 inch black spines which radiate out around the length of the main trunk. This feature is curious because the Hawaiian Islands had no natural herbivores to eat the bark. Why would it evolve with spines?

Currently the wili-wili tree is endangered because the small wasp that pollinates the tree is threatened by invasive wasps which compete with them.

Americas

The arid biome with all its plant diversity is something shared by Americas, Africa and Madagascar. There are several fine examples of plants growing in the near-desert conditions within the Koko Crater.

Plumeria blossoms are the quintessential flower for many of us when we think of Hawaii. We see it on the label of so many Hawaiian products along with native hibiscus blossoms. Plumeria flowers are popular for making flower leis. The trees are relatively small in size, and therefor popular in private gardens. But the tree is actually from South America. It was introduced by Dr. Wm Hildebrand in the 1860's. The Latin name is Plumeria pudica, it is in the dogbane family of Apocynaceae. The plant is well adapted to semi-arid conditions.

Plumeria pudica

The Koko garden has a collection of large agave plants. In past visits to Hawaii I've seen agave growing in the wild on exposed cliffs on Kauai, so I can say they've become naturalized (or invasive depending on your point of view). The foxtail agave is a popular plant in private gardens. I'm not sure there ever was a commercial use for them in Hawaii. They are originally from Mexico so perhaps they're used for fiber and tequila fermentation when produce in numbers.

Agave attentuata (fox tail agave)

Ponytail palm, seen here with saguaro and golden barrel cacti (photo courtesy of Tom Wilson)

Ponytail palm (Beaucarnea recurvata) is also native to central Mexico. In Hawaii as in most places in the world it is a popular ornamental plant and houseplant. Here in the Koko Crater garden it has grown to a large size worthy of its other nickname - elephant foot palm.

parasitic cactus

Epiphytic cactus in an ironwood tree

Selenicereus ocamponis, moonlight cacus, is a genus of epiphytic cacti that clamber up trees and rocks for support. They originated in Mexico. The plants may or may not have spines depending on the species. Often they are called moonlight cactus because they bloom at night, probably to attract bats as pollinators. Some species produce edible fruits sometimes known as dragon fruit or pitaya in Spanish. The above photo is taken of a medium sized ironwood tree that is essentially covered by this cactus from root to stem. I'm not sure how the tree survives the invasion. Another example of this plant has a large minivan-sized boulder completely covered by this cactus.

Lithophytic moonlight cactus on a lava boulder (Selenicereus species)

Africa and Madagascar

Koko crater's arid climate is particularly suited to desert-like plants from Africa and Madagascar. Here are a few examples from Madagascar that are thriving in this garden:

Madagascar 'palm'

Madagascar palm tree is not a palm. It is a succulent tree in the dogbane family of Apocynaceae. Photosynthesis mainly occurs along the trunk with relatively few leaves at the tree top (possibly to conserve water from evaporation through the leaves). It is said to have very fragrant flowers. The trunk is covered in sharp spines up to two inches in length. It is popular in gardens that are frost-free, and it can be grown as a house plant if it gets full sun.

Alluaudia procera

Alluaudia is a genus native to Madagascar. They are in the in the succulent family Didiereaceae. In gardens they are popular as ornamental plants. They feature both spines and small thick leaves running up and down the branches.

Welcome libation

A few miles from the desert bowl of Koko Crater lies a small boat harbor. On the edge of the harbor is one of the Kona Brewery establishments where a cool brew was medicine after a parching walk. As we sat and enjoyed the view - and the brew - we paused to appreciated the our experience in the Koko Crater Garden.

Kona Brewing Co., Koko Head harbor