A Potpourri of Pandans

The Tropical Garden, Fall 2016

By Chad Hudsby

The Genus Pandanus

Pandanus plants (family Pandanaceae) are distinctive woody monocots of the tropics and subtropics, ranging from West Africa through Asia and the Pacific all the way to Hawaii and Pitcairn Island. They grow as trees or shrubs in diverse habitats from the seashore to swamps, riversides, and forests. There are about 450 species known and new species continue to be discovered.

The largest species can reach 60 feet or more in height, with leaves 15 or more feet long. As monocots (like palms and bamboos), they lack the secondary woody growth produced by most trees, so their stems do not continually increase in diameter as they grow. The tight spiral arrangements of their leaves leads them to be called “screw pines” or “screw palms,” though they are often simply called “pandans.” This spiral pattern remains imprinted on the stems in the form of leaf scars after the leaves are shed.

Many Pandanus exhibit branching, which is constrained by the inability of their stems to increase in diameter with secondary woody growth. Some species have a marked difference in orientation between an upright central trunk and horizontal branches, creating architecture not found in any other woody monocots and leading to surprising similarities with woody trees. This differentiation can be so great, with horizontal branches that cease growing once they reach a certain length, that some species in Madagascar develop a very regular architecture resembling conifers. Other species are either solitary or form clumps of unbranched trunks, their architecture much like that of typical palms.

A distinctive feature of this genus is the large aerial (stilt) roots that emerge from the trunks of most species. These roots can form a dense skirt around the trunks, providing benefits in trunk support and water transport while leading to a quite ornamental effect. Male and female flowers are borne on separate plants. The flowers are small and lack petals, but often show large, dense and distinctive arrangements. The fruits are borne on large pineapple-like infructescence that can be quite colorful when ripe.

Pandanus Ethnobotany

Humans use Pandanus species in a number of ways. In Hawaii and the Pacific, the sweet fruits of Pandanus tectorius are eaten raw or cooked, as are the tips of stilt roots. A few other species also have edible fruits. Pandanus odorifer has edible seeds. Pandanus amaryllifolius, a small species often called simply ‘pandan,’ is used in Southeast Asian and Indian cooking. Its leaves are aromatic and lend a special flavor to rice and curry dishes. It is also used in desserts, often giving them a distinctive green color. An extract derived from Pandanus flowers is also used in Indian cooking. The leaves of P. tectorius and other species are used for weaving mats, baskets, fishing nets and ropes. With their distinctive forms and dramatic stilt roots, Pandanus are also widely planted as ornamentals in the tropics and subtropics. Pandanus utilis is frequently used as an ornamental in South Florida.

Dr. David Fairchild and Pandanus

Dr. David Fairchild was very interested in Pandanus. He especially came to appreciate them during his great Cheng Ho Expedition in 1939-1940, when he found several very promising species for ornamental and culinary use. He wrote about them in multiple publications:

We had not gone more than a hundred yards when we came upon the most amazing and the most lovely pandan I had ever beheld. The pandans are allies of the palms and for that reason we were quite as anxious to get them. They are handsome objects in the landscape, especially when their large rough fruits have turned golden-yellow or scarlet. Here was one rising from the bank of the stream sixty feet in the air, with a smooth trunk from one and one half to two feet in diameter. It reminded us of a Royal palm, but had a crown of narrow strap-shaped leaves that were each twenty feet or so long. The fruits had all ripened and fallen to the ground, breaking up into the long, wedge-shaped nuts of which they are composed. We collected a lot of these and Marian had a time scraping all the juicy flesh off them. Young trees of this beautiful species are now growing on filled land in the Department of Agriculture Garden at Chapman Field, but they have not yet weathered one of the cold winters we sometimes have in Florida.

~”Garden Islands of the Great East”

(The Heart of the Moluccas)

With the pandanus we had better luck. Already, plants three or four feet high are growing in Florida gardens. As they are long-leafed and quick-growing, and bear decorative, bright- red cluster-fruits they are sure to find their place in our ornamental horticulture. I was disgusted to find, however, that the plants of the species of pandan which Mr. Turno and Prof. Curran bot had growing beside their doors, the leaves of which they put in the pot and boil with the rice to give  a fine flavor, died on the way home.

~”Garden Islands of the Great East”

(Zamboanga and Mindanao)

The drooping flower cluster of the pandan does not recall to me anything else in the whole plant world. Masses of yellow flowers sit in the axils of long, white, leaf-like spathes. […] In New Guinea, Dr. L. J. Brass reports, there are pandans a hundred feet tall, and the Papuans depend on their immense fruits for food.

~”The World Grows Round My Door”

Pandanus in the Garden

Fairchild currently has seven identified species of Pandanus planted in the Garden, along with several Yet-to-be-identified species. All but a handful are in the Lowlands due to their affinity for water. The known species in the garden are: P. dubius, P. odorifer, P. solms-laubachii, P. spiralis, P. tectorius, P. utilis and P. vandermeeschii. A large planting of diverse species follows the shore of Pandanus Lake. The oldest surviving Pandanus in the Garden, P. tectorius, was acquired in 1961. Students at the Biotech @ Richmond Heights high school are using Pandanus to study root growth. The accessibility of their large aerial roots provides an exciting opportunity to investigate an aspect of plant growth that is usually hidden beneath the soil.

New introductions from plant exploration

Recent Fairchild collecting trips to the Far East and Hawaii have begun a new phase expansion of Pandanus collection. Our 2013 Hawaii expedition yielded two new species, one of which is the especially ornamental Pandanus vandermeeschii of Mauritius, which has red-edged leaves. This striking species was shared with the Garden by the Waimea Valley Arboretum and Botanical Garden.

From last year’s trip to Thailand, we brought back cuttings of a lovely silvery-glaucous-leafed Pandanus from Nong Nooch Tropical Botanical Garden. It that has rooted well and will soon be planted in the Lowlands. Our collaboration with Nong Nooch also yielded seedlings from a very large-leafed, tall, species from southern Thailand with colorful leaf bases; it was offered in the Members Day Plant Sale this year, and will soon also find a home in the Lowlands. We also obtained propagations of Pandanus amaryllifolius, giving us the opportunity to try fresh pandan leaves in cooking.

From Singapore Botanic Gardens, we obtained cuttings of Pandanus pygmaeus that are doing well. This species creates a delightful miniature Pandanus form less than 3 feet high, complete with stilt roots. Also from Singapore Botanic Gardens, we received an elegant and mysterious silver-blue leafed Pandanus that does not form a trunk. Since we have not yet examined its inflorescence, we are not entirely sure it is a Pandanus; it may, in fact, belong to the closely-related genus Benstonea—which would be completely new to the collection.

Pandanus is a large and fascinating group of plants, with many species that would be wonderful additions to the Garden. We look forward to finding more exciting introductions during our future travels to the East.