Native to the coastal savannas and hills of the Mascarene Islands, bottle palm (Hyophorbe lagenicaulis) is not tolerant of frosts. However, it is appropriate for outdoor gardens in U.S. Department of Agriculture Hardiness Zones 10 and warmer. Slowly growing to a mature height 15 to 20 feet, this palm is easy to remember because of a swollen trunk base that is as wide as 2 feet in diameter. This palm excels in sandy soils rich in organic matter.
Bottle palm is endemic (native only to a specific area) to Round Island and Mauritius in the western Indian Ocean. It is highly adapted to the growing conditions on these tropical islands, including the sandy soils, salty winds and alternating cycles of wet and dry seasons.
Being isolated from other plants' genetic lineages on the Mascarene Islands far from Africa, bottle palm survived for centuries in this region with a small human population. Reliance on seasonal rains and seasonal drought, wind and a warm maritime tropical climate resulted in it becoming a distinct species with little tolerance for growing conditions that do not mimic its natural habitat.
Noteworthy adaptations of the bottle palm include a swollen trunk that conserves water during droughts. The trunk's bottle-like form is accentuated when there is pronounced alternation between a warm, wet summer season and dry winter. This is especially true in tropical garden environments where irrigation and richer soils predominate. The palm also has thick, stiff and waxy fronds to shun salt spray and conserve water. There are rarely more than five or six fronds at any one time according to the authors of "An Encyclopedia of Cultivated Palms." The fronds' leaflets are oriented in an angular fashion so that in cross-section they look like a "V." This orientation captures sunlight at various angles at cooler times of day rather than flatly positioned to the sun at midday.
Today, bottle palm is an endangered species on the Mascarene Islands. Round Island is uninhabited, but historically Dutch explorers introduced pigs, goats and rabbits into the region as a source of free-range food. These animals grazed upon young bottle palms and ate their fruits, limiting the number of seeds naturally dispersed by native birds. Research by the National Trust (UK) suggests bottle palm relied solely upon birds (not wind) to spread seeds across the small island chain. The architectural beauty of this palm captured the eye of man and became an attractive ornamental plant. Bottle palms are grown around the world and are propagated by seeds produced in gardens, not harvested from the wild.
While bottle palm may be disposed to sandy soils and seasonal drought, its genetic isolation and evolution in the Mascarene Islands finds it intolerant of cold temperatures. This species tolerates temperatures as low as 30 to 32 degrees Fahrenheit without plant death. However, according to Jungle Music Palm and Cycad Nursery, frond damage occurs at temps as cool as 38 degrees Fahrenheit. This palm also doesn't cope well to shaded landscape exposures or wet soils. Prolonged drought will also kill the palm even though water reserves exist in the trunk.