Tropical Gardening: Many South Pacific plants find homes in Hawaii

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

Next year, several members of the Hawaii Chapter of the International Palm Society are about to find out. The Society is having its 2016 biennial conference and tours in Singapore, Borneo and tropical northern Australia. Members will not only meet palm growers and enthusiasts, but will collect new palm species for Hawaiian gardens.

The conference and field study will start June 12, 2016, in Sarawak, Borneo, and conclude with travel to far north Darwin, Australia, via Singapore.

Australia, Borneo, New Caledonia and perhaps islands such as New Zealand and the Fiji group are thought to be part of the great continent known as Gondwana and have 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 tolerant of moisture extremes.

In the drier parts of our island, waterwise gardening starts with planting drought-tolerant plants. Many palms fit this bill.

Along with Hawaiian native plants, they can help cut our water bill. For example, we can use our native Pritchardia or loulu palms but also Pritchardia thurstonii and Pritchardia pacifica, which are much easier to grow in difficult situations. In fact, P. thurstonii grows in profusion on small coral islets of the Lau group to the east of the larger Fiji Islands. At one time, these palms were much more common but the introduction of seed-eating rats severely limited their range.

It seems all life has cycles. Ideas, attitudes and philosophies have cycles, as well. We shift from conservative to liberal and back. Clothing styles also cycle. 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 native plants — in fact, 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 while at the same time being on the lookout for rare, beautiful and possibly endangered plants, such as those from lands south of the equator, to enhance our local landscapes. Some of these can grow where nothing else will.

Hawaii landscapes are well-known for their varied and unusual plant life. Many of these plants were introduced from the West Indies, South America and Africa. But few plants have adapted themselves as well as those from the South Pacific, Australia and the East Indies.

Australia is a vast and ancient continent. 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 climactic zone imaginable in Australia, plus an extremely long period of evolution, there are hundreds of species we can grow here.

For example the paperbark tree, Melaleuca leucodendron. It long has been used here as 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, Callistemon viminalis, has the form of a weeping willow with red bottlebrush-like flowers.

The colorful bottlebrushes include the genera Callistemon and Melaleuca. 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. Flowers are followed by woody seed capsules that look like beads pressed into 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 also are 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 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 New Guinea. It is Casuarina papuana, with a broad weeping habit. In the garden, it usually grows to about 20 feet.

In Hawaiian gardens, you will find such common Australian species 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 island is the Alexandra palm, or Archontophoenix alexandrae, which also is from Australia. Another Achontophoenix is the king palm, which is more robust and adapted to elevations up to 5,000 feet. Many Australian Livistona palm species and cycads also have been introduced.

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

There are more than 700 species of eucalyptus, 200 species of grevillea, 100 species of bottlebrushes and 500 species of acacia. There also are more than 50 species of palms.

Many of these unusual and interesting plants might 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 was destroyed and conditions because of climate change are hostile.

Even though New Caledonia, Borneo and other islands to the south are thought to once have been connected to Australia, it must have been many millions of years ago. So, little is known about plant species there that palm taxonomists will be exploring for species not yet found in Hawaii.

The foxtail palm, common in landscapes today, was thought to be extinct for years. Recently rediscovered, it has become one of our most popular palms. Another recently introduced that shows great promise is the Chambeyronia macrocarpa from New Caledonia.

After this conference, it assured many more fantastic palms will follow.

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