Many Australian natives prove drought resistant


What do Australia, New Caledonia and Hawaii have in common?

Australia and New Caledonia are thought to be part of the great continent known as Gondwanaland, and hold some of the most ancient species of plants and animals known today. Surprisingly, even though Hawaii is about the youngest real estate around, the ancient species thus far introduced prove to be very hardy.

Many are found to be extremely drought tolerant.

Water-wise, gardening starts with planting drought-tolerant plants. Many Australian native plants fit this bill. Along with Hawaiian native plants, they can help us cut our water bill.

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

We shift from conservative to liberal and back. Clothing styles cycle, as well. Even landscape design and plant popularity have 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, such as those from Australia, to enhance our local environment.

Some of these can grow where nothing 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.

Australia is a vast and ancient continent. In some respects, it is the closest to the fabled “lost continent,” where the ancestors of the dinosaur era still roam.

It is a fact that this isolated land mass still contains some life-forms that became extinct on other continents eons ago. It is not surprising many plants from Australia adapt well to the Hawaiian Islands.

With every climatic zone imaginable in Australia, plus an extremely long period of evolution, there are hundreds of species we can grow here. Less than 1 percent has been introduced.

Take, for example, the paperbark tree. It has long been used here in windbreaks. It, like the eucalyptus, is closely related to our native ohia. Our native honeycreepers actually feed on the necter of these trees like they do the ohia.

I don’t usually recommend the paperbark because it is so common and the flower smell is reminiscent of cooking mashed potatoes. However, there are scores of other species, some with lavender, pink, yellow or red flowers. They vary from bushes to tall trees. My favorite has the form of a weeping willow.

In some tropical countries, paperbark is planted for reforestation purposes, since it has some commercial use. The common paperback is well behaved in Hawaii, but in the Florida Everglades, it has done too well.

This is because of the draining of that region. This creates an ecological vacuum the paperbark trees found ideal. Now, instead of sawgrass, some areas are forested with paperbark.

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. They are followed by woody seed capsules, which look like beads pressed into the bark of the stem.

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, Callistemon viminalis, bloom most of the year, and are also a source of nectar for our native honeycreepers.

Another Australian tree we take for granted in our Hawaiian landscape is the Casuarina, or Australian pine.

Named after the cassowary bird, this primitive tree is not a pine at all.

Our most common species, Casuarina equisitifolia, is extremely salt-tolerant and grows all along our beaches. One of its main advantages is that it protects other more tender plants from the strong salt-laden winds.

Again, there are many interesting species. My favorite actually comes from the adjacent island of New Guinea.

It is Casuarina papuana, with a broad weeping habit. In the garden, it usually grows to about 20 feet. It can only be propagated by vegetative cuttings here, since it does not form fertile seed.

In Hawaiian gardens, you will find such common Australians as the Queensland Umbrella tree, Brassaia actinophylla; macadamia nut tree; silk oak; banksias; acacias; Australian fire wheel; stenocarupus and Australian flame tree, Brachychiton.

The palm so common to the windward sides of our islands is the Alexandra palm and is also from the land of OZ. Many Australian Livistona palm species and cycads have been introduced, as well.

Although we have a number of Australian immigrants in our gardens, we have barely scratched the surface when it comes to the potential.

There are more than 500 species of eucalyptus, 200 species of Grevillea, 100 species of bottlebrushes (callistemon and melaleuca), and 500 species of acacia. There are also 57 species of palms.

Many of these unusual and interesting plants should find homes in Hawaii, especially as we begin to landscape in areas such as South Kohala, Ka‘u, West Molokai, Lanai and even Kahoolawe, where original vegetation has been destroyed and conditions are hostile.

Of course, like all new introductions, we need to be careful that they will not become a problem.

Ones such as the Queensland umbrella tree and Australian pine have become naturalized in some areas because they are too happy here. Cycads and most palms do not naturalize readily. The Alexandra palm is certainly one exception, but these got established in areas where native forests were cleared or damaged.

Even though New Caledonia was once connected to Australia, it must have been many millions of years ago because plant life there is very different. So little is known about plant species there that palm people are exploring for species not yet found in Hawaii.

One that was introduced and shows great promise is the Chambeyronia from New Caledonia.

It is beginning to show up in our gardens with bright red new leaves.

This information is supplied by the University of Hawaii College of Tropical Agriculture and Human Resources.

 

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