The plants you encounter while climbing Haʻikū Stairs include a good cross section of native species. As you ascend, you pass through several micro-environments, where differences in slope, soil, exposure to the wind, rainfall, and clouds combine to favor different plant communities. In these communities, you can also see how different species, and sometimes the same plant species, adapt to these differences in habitat.
The careful observer can find evidence of the dispersal, adaptation, and radiation from original forms for which Hawaiian plants are famous. There is no record of Haʻikū Valley before the original settlers modified its natural plant communities. The Kaneʻohe area was heavily populated in pre-contact Hawaiʻi, and good use must have been made of Haʻikū Valley’s forests and abundant water. Based on rainfall, one might suspect that a lowland wet forest environment existed here, with tall ohia trees, loulu (native palms), gnarled koa trees, and an understory of kolea, alani, and hoawa. These are gone now from the valley floor, replaced by a largely alien community of guavas, mango, bamboo, and octopus trees, that cast their shade over the remains of old loi along the streams. From place to place, you can find tangled stands of native hau on the valley floor, and in the lower gulleys, the Polynesian-introduced kukui tree still thrives.
The bottom of the Stairs is at an elevation of about 120 meters (400 feet) above sea level. Ascending, we encounter some of the native plants now missing from the valley and find others that live only on the high ridges and in the cloud forest. We make use of common plant names in this brief tour, unless scientific names are needed to differentiate among plants. Where stair section numbers are used, these numbers are stamped (sometimes faintly) on the lower end of the left-hand railing (in the ascending direction). At the end of this page, there are some references for those who wish to learn more about native plants.
The Stairs begin beside a large mango tree at the base of a steep ridge. After a few minutes of climbing, the way emerges into sunlight from under a canopy of octopus trees. Ascending to a level above the H-3 freeway, you soon reach a steep, narrow, rocky, and windswept ridge, a favorite turn-around spot for those who find they do not like heights. Only a few hundred feet above the valley floor, this harsh windswept environment of hot sun and poor soil provides a suitable foothold for adapted native plants, including a ground cover of akoko, pukiawe and ulei, a native member of the lilly family uki uki, and the indigenous fern palapalai. Ti, the small indigenous tree, lama, and the occasional fragrant maile grow on the lee side of the ridge. A few stunted ohias adorn the windward slope. Look for these along stair sections 36 to 70.
Among the stories revealed in climbing the Haʻikū Stairs is that of plant adaptation, variation, and speciation. How does a plant species, once arrived on an island, reproduce, adapt to its new environment, and spread to yet unfilled ecological niches? The common ohialehua is an interesting example, with a scientific name, Metosideros polymorpha, that indicates the many forms this member of the myrtle family has taken since arriving in the islands. Quite a few of those forms, arguably in different species or variations, take shape along the Stairs (M. polymorpha, M. tremuloides, and M. rugosa). See if you can spot them.
Ascending above the first cliff band, the line of the Stairs passes into the shelter of a hanging valley. Hot and sultry in the sun, this protected valley has better soil and shelter from the harsh, persistent trade winds that flow over the ridges above and below. In this more hospitable environment, alien guavas and octopus trees once more make an appearance. Here, the bane of hiking trails throughout the islands, Clidemia hirta, an aggressive alien weed transmitted by seeds on hikers’ boots, proliferates along the Stairs. Despite these invaders, endemic kolea, a grove of mamaki, which is a small tree with light green leaves, and an endemic fern, amau, are found here. Look for these along stair sections 157 to 210.
Just before emerging from the hanging valley onto the ridge, the Stairs pass through a bunch of uki (not to be confused with uki uki), an endemic sedge. This interesting plant has long, grass-like leaves and brown flower stalks. Look for these on stair section 225.
The Stairs, now at an elevation of over 500 meters (1,600 feet), follow the main mountain ridge, fully exposed to the trade winds. Here the plants are adapted to a cliff habitat, and with progress along the ridge ascend, as does the climber, into nearly perpetual clouds.
Look for M. tremuloides, known to Hawaiians as ahihi; note the small, narrow trembling leaves on reddish leaf stems (petioles), with the familiar lehua-shaped flower. This is a variant or closely related species of ohia lehua; also look for ohia rugosa, with lumpy, convex leaves, known to Hawaiians as lehua-papa. Although they differ in leaf detail, an inspection of their flowers will reveal that they are quite alike. The attractive, bright red lehua blossom has evolved for pollination by birds. Look for the ahihi on stair section 258.
Conversely, inspect the drab monono: its tiny, pale green trumpet-shaped blossom did not evolve to be attractive, but to be pollinated by the wind. This plant of the coffee family is related to the nearby kopiko, with clusters of small white flowers growing in a group from the center of terminal leaf clusters.(Notice the bumpy Clidemia leaves behind the kopiko flower head in the linked image.) Both are in the family Rubiaceae, which is well represented along Haiku Stairs. Look for these along stair sections 323 and 330.
The native palm tree loulu makes its appearance on these upper ridges, protected here from rats that predate upon their seeds in the lowlands. The Hawaiian hydrangea, kanawao, is plentiful along the upper Stairs, its clustered purple flowers revealing its continental heritage. And look for the kolii, a Trematolobelia, a small plant with clustered narrow leaves at the top of a stem, shaped like a tiny palm tree. It flowers once and dies, leaving multiple bare stalks projecting upwards like a blown-out umbrella. Seeds are then scattered downward by the wind from the hollow “shaker” seed pods. Look for these plants at stair sections 359, 387, and 441.
This brief narrative has just skimmed the surface. We’ll leave you here, near the summit, with this short sample of what plants may be found along Haiku Stairs. Be careful on the way down.
Over 50 native vascular plant species have been identified near the Stairs, and no one has yet attempted to catalog the epiphytic plants (plants that grow on other plants) which proliferate in the cloudy realm at the top of the Stairs.
For those with an interest in learning more about native Hawaiian plants, the following two books are worth your while:
For field identification:
A Hiker's Guide to Trailside Plants in Hawaii; J Hall, 2004 and, A Pocket Guide to Hawaii’s Native Trees and Shrubs; H. Douglass Pratt; Mutual Publishing, 1998
For ecological interpretation and natural history:
Hawaii, A Natural History; Sherwin Carlquist, The Pacific Tropical Botanic Garden; 1980.