Landscaping for tropical ambiance

We create moods by the kinds of plants we use in our garden.

Cactus and succulents, plus lots of bright colors, make a garden feel hot and desert-like. Pines, cypress and other cool-climate plants create a Pacific Northwest look.

While traveling through Britain and Switzerland on the way to an International Palm Society meeting in the Canary Islands, I was surprised to see palms, bamboos and other tropical plants used to create special effects in private and public gardens. The effect created with palms in northern California or along the French and Italian Riviera is misleading. These regions have wet and cold weather several months of the year.

The air of freedom and informality in Hawaiian gardens is partly the result of the exotic plant materials used. The “hang-loose” style of design mixes bold and colorful shrubs, ground covers and trees in a relaxed, unregimented manner.

Local garden design springs from the Hawaiian love for plants and a “more, the bettah” philosophy. It also develops from the giving nature of local folks. A plant is an appropriate gift for any occasion. Before long, the garden and home burst with luxuriant vegetation.

To develop that tropical look in cooler climates, the selection of materials should be those with a bold tropical presence. Here are some tips for your mainland friends who want a touch of Hawaii at home. Sumac and Ailanthus altissima, or tree of heaven, are hardy trees with a tropical look. The latter, introduced from China, is so well-adapted it has become naturalized in some parts of North America. Yet it resembles tropical trees such as the African tulip with its bold compound leaves.

Another tree, not quite so common or hardy, is the Albizzia julibrissin, or Persian silk tree. Although tropical in appearance, with poinciana-like foliage and pink pompon flowers, this tree will tolerate conditions below 0 degrees. The tree can reach heights of up to 40 feet but usually spreads out like an umbrella to 20 feet. It makes a good patio tree.

The Ginkgo biloba, or maidenhair tree, is another “toughie” from China that will tolerate sub-zero temperatures. This tree is a living fossil from the era when tree ferns and palms grew throughout North America. It is popular in urban areas because of its adaptability to harsh conditions.

A tropical-looking garden must have palms, tree ferns and bananas, and some are fairly hardy. If you live in an area where temperatures seldom reach 10 degrees or colder, the Trachycarpus fortunei, or windmill palm, is great for the ultra-tropical look. It is fast growing to about 30 feet. This palm should be used in groups of three to seven for a dramatic effect. The many healthy specimens in Seattle attest to this tree’s ability to withstand cold. Another much slower palm that is equally hardy is the Chamaerops humilis, or European fan palm. This clumping type has been known to sustain temperatures of 6 degrees above zero. Several other palms grow as far north as coastal Oregon.

Hawaii’s tree fern is much too tender to grow out of doors except in the most protected areas of the South. A close relative from New Zealand is much tougher and will take temperatures down to 20 degrees. The New Zealand tree fern, or Dicksonia antarctica, can be grown in protected coastal areas of Washington and Oregon. They are slow growing but will attain trunks of 15 feet with cool, moist conditions.

Many hardy ferns may be used as ground covers to enhance that tropical look in even the coldest gardens.

I saw a Japanese species of banana, Musa basjoo and Musa sikkimensis, growing in London. These bananas are root hardy and regrow every year even after freezing to the ground in southern England, southwestern Canada and on the East Coast to Long Island.

Several hardy bamboos will take temperatures near zero.

Close relatives of bamboo such as arundo or Spanish cane can be used where temperatures are below zero. Although this giant reed may freeze in winter, with a protective mulch and good soil, it will grow from 6 to 15 feet in a summer. Another popular bamboo relative is pampas grass, or Cortaderia sellowana. This versatile clumping grass tolerates dry to wet soils and temperatures close to zero if protected by mulching.

Nandina domestica is a bamboo lookalike. This evergreen loses leaves at 10 degrees and is killed to the ground at 5 degrees, but usually recovers. In milder areas, the plant grows slowly to about 8 feet and makes attractive patterns against a wall. It is also used as a container plant in the home.

The list of tropical lookalikes goes on. Consider cider gum and snow gum, which survive temperatures close to zero.

Fig, pomegranate, olive and loquat can be found growing as far north as Seattle.

Your mainland friends can experiment with these and others that nurseries and garden centers carry in their area or try some from more southerly locations. You can increase hardiness by plant conditioning and protection.

Avoid heavy fall fertilization, but remember an underfed plant is prone to damage.

Place marginal plants where they will take full advantage of the warmer microclimate in the garden. Temperatures are often warmer on the south sides of buildings, sheltered from cold winds.

Mulch tender tuberous plants. This protects the soil from freezing. Even Hawaiian taro can be grown in this manner. I once saw a large clump of taro in a garden in Washington, D.C. Mulching with composted manure was the gardener’s secret. Trees like windmill palm can be wrapped with burlap or other protective material during extremely cold weather.

Folks on the mainland can use imagination and have a luxuriant garden. Experimentation with new plants will make them the talk of the neighborhood.