Tropical Gardening: Rapid ohia death now found throughout island forests

  • Courtesy of VOLTAIRE MOISE Rapid ohia death is now infecting the forests of West Hawaii. It is especially evident when driving up Kaloko Mauka above Kailua-Kona.

Rapid ohia death has been spreading in the forests of East Hawaii for several years. Now it is showing up in North and South Kona as well.

To see the effects of rapid ohia death, take a drive up Kaloko Mauka and you will see defoliation and die back on trees young and old. The fungus attacks the leaves and causes premature leaf drop. It is similar to the disease that killed most rose apple trees in East Hawaii.

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If the weather continues to be wet, it is likely we will see more diseases in the normally cool areas of the islands. For example in Kaloko Mauka, we are seeing fungal diseases attacking palms such as the Howea forsteriana that did quite well until the recent rainy trend.

The question is what will our forests look like in 30 years or more with the vacuum created by dying trees?

If we look back at the time the first humans arrived almost 2,000 years ago, our forests were very different. Vast Pritchardia palm forests covered the highlands and the lowlands alike. No one knows how many species were present. Today 24 species remain and they are rare in the wild because of rats and pigs eating most seed produced.

When it comes to ohia, we have had big die-outs in the past, but none so potentially devastating as rapid ohia death.

But if we are to continue to have forests and viable Hawaiian landscapes we will need to recognize they will be very different than in the past. Nature might replace ohia with other pioneer species with or without human intervention.

It seems all life has cycles. Ideas, attitudes and philosophies have cycles as well.

We shift from conservative to liberal and back. Clothing styles cycle as well. Even landscape design and plant popularity has cycles. Often, these swings of the pendulum hit an extreme before a movement back in the other direction.

In plant use, we are swinging toward using local, native plants, and a few landscape designers are using only native plants. This is exciting since native plants have been ignored for a long time. It is important to protect and use our native plants in the landscape and at the same time be on the lookout for rare, beautiful and possibly endangered plants to enhance our local environment. Some of these can grow where little else will.

Hawaii is well-known for its varied and unusual plant life. Many of these plants have been introduced from the West Indies, South America and Africa. But few plants have adapted themselves as well as those from tropical and subtropical Australia.

Take for example the genus Melaleuca. Like the eucalyptus, paperbark, bottlebrushes, allspice, mountain apple and guava, it is closely related to our native ohia. Our endemic honeycreepers actually feed on the nectar of these trees like they do the ohia.

Paperbark, or Melaleuca leucadendron, is not recommended because of its tendency to naturalize in marshy areas. However, there are scores of other Melaleuca species, some with lavender, pink, yellow or red flowers. They vary from bushes to tall trees. One favorite has the form of a weeping willow.

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The colorful bottlebrushes also include Callistemons. Dozens of species are available in Australian nurseries varying from small evergreen shrubs to large trees. Their flowers are made up of clusters of stems that look like the common kitchen bottle cleaner. Flowers vary from white and yellow to pink and red. Advantages of the bottlebrushes are their insect and disease resistance, their tolerance of drought and wet conditions and their overall attractive appearance. Some species such as the weeping bottlebrush, or Callistemon viminalis, bloom most of the year.

Whatever the future brings to Hawaii forests and gardens, we can be assured it will be very different than what we see today. The important thing is that Hawaii remains “Clean, Green and Beautiful.” This great motto is memorialized by the Outdoor Circle, which continues to play an important role in keeping Hawaii from becoming the concrete and asphalt blight that plagues so many urbanized parts of the mainland.

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