Plants of Hawaii Volcanoes National Park

Scientific Name Metrosideros polymorpha Gaud.
Family Myrtaceae (Myrtle family)

Other Names Hawaiian: `ohi`a, `ohi`a lehua, lehua (there are a number of variations on the Hawaiian names)
Status Endemic
Distribution & Habitat Near sea level up to 2,200 m.

Found on all the main islands except Ni`ihau and Kaho`olawe.

Locations in this Guide Devil's Throat, Puimau Hot Spot, Mid-Elevation Woodland, Thurston Lava Tube, Park Headquarters, Observatory, South-West Rift Zone, Kipuka Puaulu, Ola`a Forest, Mauna Loa Strip Road, Top of the Strip Road, Sulphur Bank
General Appearance
This is an extremely variable species, with mature plants ranging from a few centimeters tall to tall forest trees.

The photo on the right shows several trees in the open area in front of Kipuka Puaulu.

 

 

Kipuka Puaulu

Observatory

South-West Rift Zone

South-West Rift Zone

Kipuka Puaulu

Mid-Elevation Woodland (on 1974 flow)

Mid-Elevation Woodland (on 1974 flow)
The trees can get very large, as shown by the size of some of the trunks (both from the same tree) shown below.  Unfortunately, this large individual has recently died.

Kipuka Puaulu

Kipuka Puaulu
The large trunk below is hollow, but the individual survives. 
The `ohi`a forest at the intersection of the road from Hilo at the Park entrance shows a good example of a stand of medium-stature trees with a closed canopy and a tree-fern understory. Park Headquarters
Trees in different environments can take on a very different appearance.  The tree on the right is from the 7,000 ft elevation near tree line. Top of the Strip Road
The bark on the trunk is usually rough. Kipuka Puaulu
Leaves
The general appearance of the leaves shows how they are arranged in pairs and are opposite each other.

The shape of the leaves is variable as is the color.

 

Volcano Observatory
Thurston Lava Tube Thurston Lava Tube

South-West Rift Zone

Top of the Strip Road

Puhimau Hotspot

Some leaves, such as those in areas with highly acidic rainfall, may be red.

South-West Rift Zone
Newly emerging leaves can also be reddish. Sulfur Banks
In some areas, the leaves are pubescent.  There may be a number of functions served by the fine hairs including protecting the leaves from excessive radiation at high elevations to enhancing precipitation by trapping moisture from low-lying clouds. Top of the Strip Road
Top of the Strip Road Top of the Strip Road

The abundant litter from the mid-elevation dry forest shows (below) the distinctive shape of the M. polymorpha leaves.

Mid-Elevation Woodland
Galls, produced by an endemic psyllid, at common on `ohi`a leaves in some areas.  Note this particularly in the Mid-Elevation Woodland and at Sulphur Banks.

Mid-Elevation Woodland

Mid-Elevation Woodland

Flowers & Fruits
The plant at the right is just about ready to flower. Top of the Strip Raod
The bright red flowers are very obvious, even from a distance. Volcano Observatory
Sulphur Banks Sulphur Banks
Volcano Observatory Park Headquarters

Observatory

Observatory
Sulfur Bank Sulfur Bank
Mid-Elevation Woodland (on 1974 flow)
Small individuals are sometimes adult plants and fully capable of reproduction.  Often, this happens in stressed environments such as near the sulfur vents at Sulphur Banks and on the recent lava flows. 1974 Flow at the Mid-Elevation Woodland Site

Mid-Elevation Woodland (on 1974 flow)

Mid-Elevation Woodland (on 1974 flow)
Phenology
Natural History There are eight varieties of M. polymorpha recognized by Wagner et al. (1990: 967).
Conservation
Miscellaneous Photos
A fire near Kipuka Puaulu in July, 2000, has cleared the grasses and shows how several individual trees appear to have grown from a fallen individual. July 2000 fire near Kipuka Puaulu
You can see the same process of branches growing from a downed trunk in the rainforest.  The trees on this trunk, which is off the ground because it has snagged another tree, reach all the way to the top of the canopy.  This tree fall must have happened a long time ago. Thurston Lava Tube
Thurston Lava Tube Thurston Lava Tube
The trees below show how trunks can join.  The trees below, right, form a straight line that may have been the result of either early epiphytic establishment on a now decayed log or perhaps growth starting as branches from a downed tree.
There are several very large `ohi`a trees in the background of this picture that have recently died.  This area has been drier than usual and had an outbreak of the two-spotted leaf hopper.  Apparently this combined stress has been too much for many of the trees in this area in and adjacent to Kipuka Puaulu. Kipuka Puaulu

Mauna Loa Strip Road (near Kipuka Puaulu)

Aerial roots are sometimes abundant on an individual.  They may serve as a way to filter precipitation from passing clouds. Thurston Lava Tube
Mid-Elevation Woodland Mid-Elevation Woodland

Thurston Lava Tube

`Ohi`a roots penetrate into the lava tubes and provide a source of food for the cave animals.  The roots on the right are in Thurston Lava Tube. Thurston Lava Tube (inside)
Most of the `ohi`a seedlings that survive start out growing as epiphytes.  Here they are on log from a downed tree.  If they get larger, their roots may eventually reach down to the forest floor. Olaa Forest

Thurston Lava Tube

`Ohi`a is a well-known pioneer on recent lava flows.  You can often see small plants emerging from cracks in the lava.

As these individuals get larger, they increasingly build a layer of litter.  This greatly changes the characteristics of the local habitat.

Mid-Elevation Woodland (on 1974 flow)

Mid-Elevation Woodland (on 1974 flow)

Mid-Elevation Woodland (on 1974 flow)
`Ohi`a trees that were knocked down during the lava flow decay, also contributing to a changing environment. Mid-Elevation Woodland (on 1974 flow)

Mid-Elevation Woodland (on 1974 flow)

Mid-Elevation Woodland (on 1974 flow)
Other Notes

References Wagner, Warren, Derral Herbst and S. H. Sohmer 1990. Manual of the Flowering Plants of Hawai`i. University of Hawaii Press.
Links to Other Sites

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Last Updated: 08/05/03

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