Tropical Gardening: Australia’s silver oak in full bloom in West Hawaii

Photo courtesy of Voltaire Moise The Silver Oak (Grevillea robusta) Forests of North Kona and Ka‘u are in full bloom with their bizarre orange inflorescences. Another specie with red flowers (Grevillea banksia) is rare but found in parts of Ka‘u near Pahala. These trees have naturalized in abandoned pasture lands to the point we take them for granted but enjoy them just for their beauty.
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April showers bring May Flowers. Some in Hawaii are from Australia. When it comes to strange animals and plants, Australia is in the lead for its share of the unusual to unique. This ancient mini continent has mammals that lay eggs to the marsupials that carry their premature babies in pouches. Recent fires put many in the animal kingdom at risk and the plant kingdom as well. Some Australian ecosystems will be altered for centuries and some may never recover.

Even though there are many species yet to be discovered, it is fortunate that some of the more valuable plants have been introduced to Hawaii before their demise. Some introductions have found Hawaii so inviting that we consider them weeds. A better definition for them could be pioneer species that are attempting to heal the wounds that Man and Nature have created. The octopus tree (Schefflera actinophylla) and the silver oak (Grevillea robusta) are two examples. They tend to readily grow where the land is disturbed. If we were to be careful in protecting our native landscapes, trees like these would not be a problem. Be it as it may, let’s take a moment and forget their robust tendencies and appreciate them for their beauty. The silver oaks with their bizarre orange inflorescence may be seen in full flower along the Mamalahoa Highway in West Hawaii. Try to appreciate them from an artist’s perspective and recognize that they are like other trees, sequestering carbon and producing oxygen.

The Protea family is primarily found south of the equator in Africa, South America and Australia. It includes the genera Macadamia, Banksia, Grevillea, Hakea, Hicksbeachia and Stenocarpus. Of all the many floral choices available in the marketplace, none can beat the bizarre yet enhancing beauty of the Protea family. From the robust, intense-colored sunburst pincushion to the deceiving duchess, that looks more like feathers than a flower, Proteas resemble no other flowers in the world. Even the common reforestation tree, silver oak, Grevillea robusta, has a striking inflorescence.

One of the people responsible for Hawaii Proteas was Dr. Philip Parvin, horticulturist with the University of Hawaii’s College of Tropical Agriculture and Human Resources, who directed the Maui Experiment Station.

When Parvin first became director in 1968, he was highly impressed with the obvious superior growth of Proteas that had been planted at the Kula station three years earlier. As he was familiar with Proteas being grown in California, he was inspired to explore the potential of a Protea industry in Hawaii.

With partial funding for Protea research coming from the Governor’s Agricultural Coordinating Committee, several College of Tropical Agriculture and Human Resources researchers have been able to solve some of this young industry’s problems and help improve production and handling. Dr. Parvin worked on the management aspects of the crop, such as the selection of superior cultivars, propagation, density spacing, pruning, and plant nutrition.

Dr. I-Pai Wu, a professor of agricultural engineering, developed drip irrigation systems to meet water requirements in the field and to make better use of available water resources. John Cho, Stephen Ferreira, and Norman Nagata, plant pathologists, examined fungicides for the control of root rot, a disease problem in Protea production.

Ronald Mau and Arnold Hara, entomologists, helped to solve some of the pest problems, including those that could lead to the rejection of shipments to other areas. Dr. Philip Ito, a Hilo based horticulturist, worked on new types of protea for the world market.

Dr. Robert Paull, a plant physiologist, solved problems arising during shipping and ways to extend protea shelf life. So you see that the intriguing Protea family blossoms on display in homes and places of business such as hotels didn’t just happen. They are the result of concerted efforts by Hawaii’s agricultural scientists and growers working together to develop another fine Hawaiian grown product with tremendous potential.

Most Proteas require cool climates on the dryer side like Waimea, Volcano, West Hawaii, Ka‘u and Maui. They prefer well drained soils. When grown in wet or humid locations, disease and pests become a problem.

Even if you are not interested in growing Proteas commercially, you can be certain that these gorgeous and exotic flowers are perfect to enhance your home, garden or a special, long lasting gift. If you receive some as a gift, remember that Proteas have another advantage besides their remarkable attractiveness. They can be easily dried and enjoyed for a long time to come. All you have to do is remove the water from the container when the flowers start to lose their freshness and allow the flowers to dry into a permanent arrangement.

Another method is to hang the flowers upside down for about a month, and then use them in a dry flower arrangement.

If you are not familiar with Protea group, ask your local florist to show you the various types now being produced, what each is called, and how long they will last.

For further information on the Protea family, contact your local UH College of Tropical Agriculture Extension Service office. Master Gardeners there can help you with pertinent information. In Hilo the number is 981-5199 or call Kona 322-4893.

Several books are available like ‘Sunset’s Western Garden Book’ to give you tips on growing these amazing plants.