Found on all the main islands except Ni`ihau and Kaho`olawe.
| 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.
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| 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. | |
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| The large trunk below is hollow, but the individual survives. | |
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| 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. |  |
| 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. |  |
| The bark on the trunk is usually rough. |  |
| 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.
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Some leaves, such as those in areas with highly acidic rainfall, may be red. |
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| Newly emerging leaves can also be reddish. |  |
| 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. |  |
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The abundant litter from the mid-elevation dry forest shows (below) the distinctive shape of the M. polymorpha leaves. |
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| 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. | |
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| The plant at the right is just about ready to flower. |  |
| The bright red flowers are very obvious, even from a distance. |  |
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| 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. |  |
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| 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. |  |
| 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. |  |
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| 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. | |
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| 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. |  |
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| Aerial roots are sometimes abundant on an individual. They may serve as a way to filter precipitation from passing clouds. |  |
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| `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. |  |
| 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. |  |
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| `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. |
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| `Ohi`a trees that were knocked down during the lava flow decay, also contributing to a changing environment. |  |
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