While designed primarily as a display garden, some areas in Allerton Garden focus on distinct collections. One section is devoted to an impressive collection of plants in the order Zingiberales, which includes Heliconia (in the Heliconiaceae), Costus (spiral gingers, in the Costaceae or Costus family), Calathea (in the Marantaceae or Prayer Plant family), and Etlingera (torch gingers in the Zingiberaceae or Ginger family).
The Palmetum contains many different species of native and exotic palms (in the Arecaceae or Palm family), including the magnificent Corypha, or Talipot palm, which flowers just once in its lifetime, producing the most massive flower cluster of any plant; the Raphia palm with giant leaves 30 feet long which yield raffia fiber; and the betel nut (Areca catechu), whose seeds are chewed in many parts of tropical Asia. Beyond the Palmetum, other members of the Palm family are found throughout the Garden. The jagged fronds of the Licuala palms (Licuala spinosa) planted adjacent to the Mermaid Fountain echo the shape of the statues’ tails. Graceful clumps of MacArthur palms (Ptychosperma macarthuri) form a lush backdrop for some of the Garden’s features.
Members of the Araceae or Arum family are in many parts of Allerton Garden. The Anthurium, which is often identified with modern-day Hawai'i, is a member of this family; a pair of giant Bird’s Nest Anthuriums, Anthurium hookeri, flank a cascading waterfall. Chinese taro, Alocasia cucullata, from Southeast Asia, is favored in Hawai'i by gardeners of Chinese descent. Alocasia macrorrhiza, 'ape or sweet 'ape, was introduced to Hawai'i.
Hillsides are planted with Cassia (trees in the Fabaceae or Pea family) of assorted hues and various species of Plumeria (also called Lei Flower and Frangipani, in the Apocynaceae or Dogbane family). Vines covering the cliffs overlooking the ocean include brilliant Bougainvillea (in the Nyctaginaceae or Four O’clock family) and Thunbergia (in the Acanthaceae or Acanthus family). Along the stream are several splendid Moreton Bay fig trees, Ficus macrophylla (in the Moraceae or Mulberry family). The enormous plank-like buttress roots that support these trees can be up to 6-8 feet high.
West of Lawa'i Stream there is a scientifically documented collection of trees, shrubs, palms, and Pandanus species from Micronesia and Polynesia used for research, conservation, and education purposes. Pandanus, called hala in Hawai'i, is a member of the Pandanaceae or Screw Pine family. An essential plant in many Pacific islands, its leaves are used for weaving mats and its juicy fruits provide a nutritious food source.