Branches of Botany: Large tropical gardens are perfect for iconic palms

Few plants are as iconic as the palm tree. Their presence lends an exotic air to logos and design motifs. In fact, it appears that members of the Arecaceae family (palm family) seem to be synonymous with anything tropical. Technically this is correct because palms are distributed throughout the tropical and subtropical regions of the world.

Surprisingly it is possible for them to thrive outside of their native range without the protection afforded from a greenhouse or plant enthusiast’s living room. There are outdoor plantings of Trachycarpus fortunei (Chusan palm) at the Logan Botanic Garden in southwest Scotland.

Here in Hawaii people can grow a wide variety of palms to include native species of Pritchardia fan palms. Unfortunately, outside the realm of botanical gardens, public spaces and private residences, only a handful of taxa are commonly used in landscaping. Most of them — save two — are native to Madagascar, Australia, New Guinea, the Philippines, Southeast Asia and other areas. The exceptions are Pritchardia pacifica (Fiji fan palm) and P. thurstonii (Thurston’s fan palm), which are native to western Pacific islands.

Pritchardia is distributed from Fiji in the west to the Tuamotu Archipelago in the east with a center of diversity in Hawaii. About 24 of the 29 accepted species occur here in our islands.

The etymology of the genus honors William Thomas Pritchard, who was a British consul in Fiji from 1858 to 1863. These solitary palms are easy to identify with their often large, fan-shaped leaves which have leaf stalks that lack thorns.

Non-native species like P. pacifica and P. thurstonii differ from their Hawaiian counterparts in that they have much smaller fruit. They are usually only fractions of an inch in width. Based on this similarity the two species are often confused. This becomes a problem because they are such a common element in our urban landscapes. Even their home ranges are confused. One resource states that the Fiji fan palm’s origin is obscure, and maybe found in Fiji or somewhere else in the South Pacific. Other sources agree that it is native to Tonga. Thurston’s fan palm originates from both East Fiji and Tonga. This similarity in habitat might be why they look so alike, but there is one subtle difference between the two.

Plants, like any organism, come in a variety of shapes and sizes. The differences can include leaf shapes, leaf margins, flower sizes or bark. Since there are so many differences, what are the most important characteristics to pay attention to? In general, differences in the flowers or infructescence (fruit clusters) take priority to leaf shape. In the case of these two palms, it is the difference in the length of the infructescence stalk that separates them. The Fiji fan palm’s is shorter and does not extend beyond the length of the leaves, while Thurston’s fan palm extends well beyond the leaf blades.

While many of us are growing herb gardens during this time, a palmery can offer the same satisfaction if you have a reasonable open space in your yard.

People have been in the business of collecting palms for quite some time. One example in Hawaii is the Merwin Conservancy on Maui. Here the famous poet W.S. Merwin amassed a collection of 2,740 individuals in his 19-acre garden. Think about planting native species first if you want to undertake such a project, albeit on a smaller scale.

Both species mentioned in this article are considered low risk by the Hawaii Pacific Weed Risk Assessment and might make interesting specimen plants in your personal palmery.

Jesse Adams is a botanist at the Harold L. Lyon Arboretum, where he works to catalogue, propagate and conserve the plant diversity found there.