Tricks for landscaping with tropical ambience

By Norman Bezona

Agricultural Extension Agent
University of Hawaii
College of Tropical Agriculture and Human Resources

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. Using pines, cypress and other high mountain or cool climate plants gives the garden a Pacific Northwest look. And chain link fences might give a feeling of safety or jail, depending on who is experiencing them!

While traveling in 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 looking plants used to create special effects in private and public gardens like Kew. In fact, the tropical effect created with palms in northern California or along the French and Italian Riviera is very misleading, because these regions have wet and cold weather several months of the year.

The air of freedom and informality in Hawaiian gardens is partly due to the exotic plant materials used. It is also due to the “hang-loose” style of design found throughout the islands. This consists of mixing many bold and colorful shrubs, ground covers and trees in a relaxed, unregimented manner. The large variety of plants utilized in any particular garden has lead to the local label of “chop suey” landscaping. Our type of garden design often grows out of the Hawaiian love for plants. This is, “the more, the bettah” philosophy. It also develops from the giving nature of local folks. A plant is always an appropriate gift for any occasion. Before long, the garden and home are bursting with luxuriant vegetation. This type of landscaping gives a sort of well maintained jungle effect.

The best part is that the hang-loose look can be done anywhere there is a place to grow things. It can be achieved with almost any plants, but 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 you mainland friends who want a touch of Hawaii at home. There are very hardy temperate trees like sumac and ailanthus altissima, or tree of heaven, that have a tropical look. The latter, an introduction from China, is so tough and well adapted that it has become naturalized in some parts of North America. Yet it resembles many tropical trees such as the African Tulip with its bold compound leaves. When used in the hang-loose design, it can be very attractive.

Another tree, not quite so common or hardy, is the albizzia julibrissin or Persian silk tree. Although very tropical in appearance, with its poinciana-like foliage and pink pompon flowers, this tree will tolerate conditions below zero degrees. The silk tree is native to Asia and can reach heights of up to 40 feet but is usually much smaller, spreading like an umbrella to twenty feet.

The tree’s filtered shade allows grass and other plants to grow underneath. It also makes a very good patio tree.

The Gingko 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 were growing throughout North America. It is popular in New York City and other urban areas because of its adaptability to harsh conditions.

Of course, a tropical looking garden must have palms, tree ferns and even bananas, and there are those that are fairly hardy. If you live in an area where temperatures seldom reach ten degrees or colder, the Trachycarpus fortunei or windmill palm is a great one for the ultra-tropical look. It is relatively 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, Wash., attest to this tree’s ability to withstand cold. In fact, I know of one specimen in Sweden at latitude 57 degrees, that is only 3 degrees from the Arctic Circle! 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. There are several other palms that will grow as far north as Coastal Oregon.

When it comes to tree ferns, Hawaii boasts of forests of them. Unfortunately, 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 twenty 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 fifteen feet if given cool, moist conditions.

Ferns are common in the tropics. There are many hardy ferns that 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, frequently planted 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.

There are several hardy bamboos that will take temperatures near zero. Close relatives of bamboo like the Arundo or Spanish cane from the Mediterranean can be used in areas where temperatures are below zero. Although this giant reed may freeze down in winter, give it a protective mulch with a good rich soil and it will grow from six to fifteen feet in a summer. Another popular bamboo relative is pampas grass, or cortaderia sellowana, from Brazil and Argentina. This versatile clumping grass will tolerate dry to wet soils and temperatures close to zero if protected by mulching.

Nandina domestica, or heavenly bamboo, is not bamboo-related but a look-alike. This evergreen loses leaves at 10 degrees and is killed to the ground at 5 degrees, but usually recovers. In milder areas, heavenly or sacred bamboo 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 look-alikes goes on.

You might consider trees like the hardy Eucalyptus species. These include the cider gum and snow gum, which survive temperatures close to zero.

In the area of fruits, the fig, pomegranate, olive and loquat can all be found growing as far north as Seattle, Wash., on the West Coast.

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. To avoid discouragement, check with garden books that cover plant hardiness. Remember, hardiness fluctuates.

You can increase hardiness by plant conditioning and protection.

Avoid heavy fall fertilizations, but also remember a plant underfed is prone to damage.

With plants that are marginal, place them where they will get full advantage of the warmer micro-climate in the garden. Temperatures are often warmer on the south sides of buildings, sheltered from cold winds.

Where possible, mulch tender tuberous plants like cannas and calla lilies. 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 this 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.