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The Poamoho Trail follows the north ridge of Poamoho Gulch from near Wahiawa to the summit of the Koolau Mountain Range at the head of Punaluu Valley. This runs through a fairly typical section of the leeward slope of the Range, in an area where the crest is low enough to permit a considerable extension of the rainy area, and consequently of the montane rain forest and moist forest, down on the leeward side. The koa zone, the lehua zone and the cloud forest zone (Hosaka 1937) are represented, the two latter rather extensively, along this route. A very good assortment of native plants may be seen, and since the return journey follows the same route, participants in the excursion may go as far as they feel inclined to and return at their leisure. The trip on foot to the summit and back is about 6 miles.
Starting from the University, the route follows Wilder Avenue, with its *Delonix regia (royal Poinciana or flamboyant) trees, past the Punahou School campus with royal palms and *Cereus undatus (night blooming cereus) hedge. On Vineyard Street it passes the Foster Garden, unfortunately now rather mutilated by the road builders, but still containing some fine trees. It is ironic that at the same time when talk about a botanical garden for Hawaii seems to be most plentiful, actions seem to run in the opposite direction, with trimming down and attrition of the rather fine, though small, existing garden.
The route leaves the city along North King Street past Moanalua Gardens, with fine *Samanea saman (monkey pod) trees, and Salt Lake Hill. This is an ash or tuff cone which has yielded some extremely interesting plant fossils that indicate an ancient forest at low altitudes.
The principal vegetation along the highway is made up of sugar cane and pineapple plantations with some *Eucalyptus plantings. The gulches have some secondary forest. Beyond the town of Wahiawa, a small side road is followed up a gentle slope through pineapple fields and grassy fields with *Panicum purpurascens, scattered Acacia koa, and many planted *Albizia falcataria trees. A gulch has a few native trees, and then the road passes a dense stand of *Melaleuca quinouenodia.
Above this is a rather altered Metrosideros (lehua) forest with a considerable admixture of planted *Eucalyptus, *Albizia and *Melaleuca, and with scattered Acacia koa locally. There are extensive tangles of Gleichenia linearis (uluhe, or staghorn fern), and *Clidemia hirta and *Pluchea odorata are common along the road. The two latter are rather recent arrivals but very aggressive. *Spathoglottis plicate, the purple ground orchid is occasional along the road, also, with *Commelina diffuse and *Panicum purpurascens (pare grass). The *Spathoglottis was accidentally distributed in the forests with nursery stock raised near cultivated *Spathoglottis in fruit. On steep banks and road cuts, Gleichenia linearis, Lycopodium cernuum var. crassifolium, Cladonia sp., *Andropogon virainicus, Sphenomeris chinensis, and Metrosideros seedlings are common. A good example of such a cut is at the end of the road.
From the road, the trail starts though a grove of Acacia koa (koa), with Gleichenia linearis on the steep bank to the left, *Rubus rosaefolius (thimble berry), with white flowers, #Ludwigia octovalvis with yellow flowers, and *Anthrostemma sp. with pink flowers, at the base, along the trail. A small landslide scar is being colonized by Gleichenia linearis, Sphenomeris chinensis, Nephrolepis exaltata (or perhaps N. hirsutula), Machaerina angustifolia, M. meyenii and Scaevola gaudichaudiana. At the bottom of a small ravine, below the trail, is a clump of#Musa sapientum (bananas, or plantains), probably persisting from the time of the old Hawaiians, who had a number of varieties of seedless bananas or plantains, doubtless brought with them from the South Pacific. At the upper edge of this ravine is a large plant of Cyrtandra cf. cordifolia and some tree ferns, Cibotium spendens. Cyrtandra is one of the genera that have proliferated into an astounding number of taxa in the islands. Immediately on the right are trees of Antidesma platyphylla and Perrottetia sandwicensis. The large vine with linear leaves is Freycinetia arborea. Then there is a large tree of Bobea elatior (ahakea) with the epiphytic entireleafed fern, Elaphoglossum reticulatum. Below are fine tree ferns, Cibotium splendens. Then there are some large Metrosideros collina trees with the tough vine, Alyxia olivaeformis (maile), prized by the Hawaiians because of its fragrance when the bark and leaves are stripped off and slightly wilted. Maile leis are about as characteristically Hawaiian as anything.
Acacia koa and Elaeocarpus bifidus (kalia) are above on the trail, and about 100 m farther on, Eugenia sandwicensis (ohia ai) on the right. *Clidemia hirta is common along the trail. Then there is a small fresh landslide scar, exemplifying one of the principal erosional processes in these, as in many other, tropical mountains. By this time, the remarkable variability of the Metrosideros must have become evident. In leaf shape and texture, and pubescence, there seems to be almost continuous variation, and the flowers in some localities vary from red through orange to yellow. No satisfactory taxonomic arrangement is available. The Hawaiian plant cannot be distinguished satisfactorily from those of southern Polynesia and New Caledonia. Actually we seem to have here one of the most gigantic and complex hybrid swarms in existence. It has, however, scarcely been studied from this viewpoint.
Where the trail crosses the ridge is a clump of a rough sedge, Gahnia beecheyi. A few meters farther on are some small Pelea clusiaefolia, then on the left a small Ilex anomala and Broussaisia arguta, with large serrate leaves. To the left is Gouldia terminalis var. coriacea. This genus is not so abundant but also presents remarkable swarms of hybrids (Fosberg 1937). Excellent shrubs of Broussaisia and Antidesma are also on the left, and to the right are Smilax sandwicensis and Gahnia. The large tree emerging from the gulch, with young growth slightly bronzed, is Pouteria sandwicensis. The trail returns to the right side of the ridge. Psychotria cf. mariniana (kopiko), and a large Ilex anomala may be seen here on the left.
About 100 m farther on is a tree of Gardenia remyi (or G. mannii) several meters off the trail in a Gleichenia linearis tangle. Here also is a colony of Gouldia terminalis var. coriacea.
On the right, at a curve in the trail, is a magnificent view of the gulch and forest. Just above this, on the left, is a shrub of Pelea clusiaefolia and just beyond, on the right, is a slender shrub of Pelea semiternata. Large Cibotium trees are to be seen here, also the tree weed Psidium cattleianum (waiwi, or strawberry guava), and *Clidemia hirta. Just beyond this, on the left, in a tangle of Gleichenia, is the remarkable Euphorbia rockii, a woody species with large leaves and very large pink capsules.
A steep slope, below the trail, is covered with Gleichenia linearis, with Gouldia, Pelea sp. Bobea elatior, and down 20 m, Scaevola mollis . Beyond this is a small landslide scar covered by Nephrolepis exaltata. *Andropogon virginicus is along the trail. Down to the right is one of Hawaii's remarkable endemic labiate genera, Phyllostegia grandiflora, also Broussaisia, a Bobea tree on the right, and behind it, a lehua tree with Lycopodium phyllanthum on the lower trunk, 100 m down in the gulch the glaucous looking tree is Pouteria sandwicensis. On the left is Gleichenia japonica and on the narrow ridge top below is Psychotria cf. kaduana (kopiko). Below on the right is an area of typical koa forest. Beyond it Gleichenia linearis and Elaeocarpus bifidus, the only Hawaiian species of this large IndoPacific genus. It is found only on Kauai, Oahu and Molokai.
Along the low part of the trail that follows is much *Psidium cattleianum and *Clidemia. Several hundred meters on, Just before a slope covered by Gleichenia linearis, Pittosporum confertiflorum is on the left and Tetraplasandra cf. meiandra on the right, the Pittosporum fairly common. Lycopodium cernuum, Wikstroemia cf. oahuensis and Scaevola mollis may be seen here. After a large mossy leaning tree and around a curve, the curious leafless mistletoe Korthalsella complanata hangs right over the trail, parasitic on Bobea. The trees have epiphytic Grammitis sp. and Elaphoglossum reticulatum.
Well beyond this large curve is another slope covered by Gleichenia linearis. Probably these staghorncovered slopes are old landslide scars. Here is an excellent view of the gulch. Epiphytes become abundant, including Polypodium tamariscinum and several species of Elaphoglossum. Then great slopes of Gleichenia, with large Bobea and koa trees. Just before an enormous koa tree on the right is a hush of Clermontia persicaefolia, one of the Hawaiian lobeliads. On the left, on the bank under Cibotium trees, are Trichomanes davallioides and Doodia kunthiana. Here is a deep ravine or artificial cut through the ridge to the left. Then there is a bare cliff with Cladonia, Spenomeria and other small plants. One hundred meters beyond this, on the right, is a bush that appears to be a hybrid between Scaevola gaudichaudiana and S. mollis, resembling the former, but with purple flowers. It is perhaps X Scaevola kahanae. At a sharp left turn, on the right, is Myrsine lessertiana in a small Gleichenia patch. Scattered along the trail is the noxious weed, *Eupatorium riparium. At the next right turn, Touchardia latifolia is on the left, Pipturus cf. albldus on the right, both endemic members of the Urticaceae. *Blechnum occidentale is on the cut bank on the left, bananas in the gulch below.
Well beyond this, on the left, is a small recess with a tree trunk with a spectacular display of Elaphoglossum sp. and the remarkable Polypodium spectrum, with triangular leaves. One hundred meters beyond this tree, on the right of the trail, is a small shrub of the rare and remarkable endemic genus of Compositae, probably Hesperomannia swezeyi. The species of this genus are very close and not well understood. Here also is a tree trunk with epiphytic Grammitis tenella, Polypodium tamariscinum and an undescribed species of Psilotum. Just beyond this, overhead, is a shrub of Dubautia plantaginea, representative of another endemic genus of Compositae. On the right is Gouldia terminalis var. terminalis, which is rather common in this area. Farther up the trail, Pelea becomes common and the related genus, Platydesma, appears.
In this area, Acacia koa remains a prominent component of the forest, locally even more common than Metrosideros. Broussaisia arguta, related to Hydrangea, is fairly common. The forest at this altitude is rather degraded and open, with a prominent undergrowth of Gleichenia linearis. That the climate is very wet is shown by the prominence of epiphytic Hymenophyllaceae on the trees.
Beyond a great new landslide area, below the trail, the condition of the forest seems better, though still not good. There is less koa here and Broussaisia is abundant. Along the trail are *Paspalum conjugatum (hilo grass), *Centella asiatica, and *Psidium cattleianum. The most common trees are Eugenia, Metrosideros, Antidesma, Acacia, Gouldia, and Perrottetia .
At a hairpin curve, on a ridge, is Leptospermum cf. scoparium. A little farther on, below on the right, is Tetraplasandra cf. meiandra with leathery compound leaves. Another araliad Cheirodendron trigynum is rare. Pelea is abundant. The tree ferns, Cibotium splendens and C. chamissoi may be seen side by side on the right, C. chamissoi being the one with stiff black hair on the stipes. Coprosma longifolia hangs over the trail. Then some large Cheirodendron trees are on the right.
Across the valley to the right, are clumps of the native fan palm Pritchardia (lolu). The species in this genus are so confusing that they cannot be identified with confidence.
After a large new landslide scar, the trail crosses to the other side of the ridge. Machaerina angustifolia is common and Bidens sp. grows on the cliff. From here on for some distance *Leptospermum has been planted on eroded areas and is locally so abundant as to be almost a pure stand. Isachne pallens is the grass on the banks. Cibotium glaucum is the tree fern on the left with a white undersurface to the frond. Dubautia laxa is on the steep slope overhead. It has broader, rougher leaves than D. plantaginea and Is a good marker of the cloud forest zone in the Koolau Range. From here on up the ridge, the dwarfed scrubby vegetation of Eugenia, Psychotria, Pelea, Gouldia, Myrsine, Metrosideros, Antidesma, and other genera, is rather typical of the cloud zone. Lycopodium cernuum and Gleichenia linearis are common in thinner places. On the ridge top Dubautia and Bidens are common, and the sprawling, slightly woody herb with large white flowers is Phyllostegia grandiflora. The trail leaves the ridge top and skirts the left side. The abundance of epiphytes on the large trees, including Polypodium tamariscinum, Elaphoglossum reticulatum, Hymenophyllum obtusum, H. recurvum, many mosses and hepatics, is characteristic of this always wet belt in these mountains.
On the high slopes along this last section of the trail is a dense scrub 23 m tall of Wikstroemia, Gouldia, Metrosideros, Cheirodendron, Machaerina angustifolia, Cyanea sp., Dubautia laxa, Sadleria cyatheoides, Gleichenia japonica, G. linearis, Scaevola mollis, Coprosma longifolia, Cibotium glaucum, Myrsine, Psychotria, Labordia, Antidesma, Broussaisia, Freycinetia, Tetraplasandra and other plants. This rich vegetation is fairly representative of the the cloud zone of Oahu. Pritchardia sp. and Trematolobelia macrostachys are occasional here. The latter endemic genus is only found in situations such as this.
The trail turns right into a ravine, its walls mostly covered by the sort of scrub described above. On a mossy cut bank above the trail is Schizaea robusta. Phyllostegia lantanoides is also found here. On the other side of this ravine is the Summit Trail which runs along the crest of the Koolau Range. Along this, about 200 m from where the Poamoho Trail joins it, there is a grassy marsh in the flat bottom of a draw. The slope to the left of this is rather peaty, with Lycopodium serratum, Sadleria hillebrandii and much Machaerina angustifolia. At the head of this draw is a small gap in the crest of the Koolau Range. This has been so trampled by soldiers in practice maneuvers that it has become very weedy.
On the crest itself, is a scrub of Vaccinium dentatum, Platydesma cornuta, Metrosideros, Broussaisia, Gouldia terminalis var. coriacea, G. st.johnii, Dubautia laxa, Wikstroemia, Labordia, Tetraplasandra cf. meiandra, Elaeocarpus bifidus, Pelea clusiaefolia, and Cheirodendron. On an open boggy ridge are Nertera granadensis, Panicum koolauensis, Plantago cf. pachyphylla, Lycopodium, Bidens sp., and Sadleria hillebrandii.
Here the weather is likely to be windy and rainy, with clouds forming as the wind rises up the tremendous cliff or pali at the head of Punaluu Valley, on the windward coast of the island. But in clear weather, from the main divide, is a magnificent view of one of the great gorgelike valleys that are characteristic of the windward coasts of the Hawaiian Islands.
Down over the edge, and on the steep slope where the trail skirts the uppermost windward slopes just below the crest, is the typical dwarfed clifftop scrub of these mountains. Among the plants one may see here are Pritchardia sp., Coprosma longifolia, C. foliosa, Pipturus albldus (s. 1.), Dubautia laxa, Machaerina angustifolia, Bidens sp., Sphenomeris chinensis, Phyllostegia grandiflora P. lantanoides, Gouldia terminalis, G. st.johnii Metrosideros, Trematolobelia macrostachya, Hedyotis centranthoides, Zanthoxylum cf. oahuensis, Selaginella menziesii, Sadleria cyatheoides and S. hillebrandii. The two latter may be distinguished by the character of the underside of the pinnules, white in S. cyatheoides, greenish and veined in S. hillebrandii. Another species, S. squarrosa, would also be expected in this habitat. It is smaller, with bullate fronds and conspicuous scales.
This summit area is fascinating and varied and would amply repay much further exploration than is possible on this excursion. It is sad that so much damage has been done by the trampling of soldiers in training, and that such weeds as *Eupatorium riparium have gained a foothold. They will doubtless crowd out many of the native plants if the trampling and other disturbances continue. *E. riparium is able to colonize bare wet cliffs even without disturbance, but on the crests it is much encouraged by the destruction of the native cover.