Sea Bean Float. Float, Bean, Float. in an Attempt to Expand Their Territory, Some Well-Armored Tropical Seeds and Fruits Hitch Rides on Ocean Currents
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SCIENCE Sea bean float. Float, bean, float. In an attempt to expand their territory, some well-armored tropical seeds and fruits hitch rides on ocean currents. These sea beans are often found on our beaches, with more than 150 different species seen from Cape Canaveral to the Keys. A seed pod’s journey across the Atlantic After dropping from their parent trees, many sea beans wash The Gulf Stream, which continues past North America, into inland rivers that flow to the ocean, where they ar e transported takes some seeds to the far-off beaches of northern Europe. by ocean currents to distant beaches. Sea beans have pockets of air that keep them afloat Those that reach shore must overcome compe- for long periods of time, and their seed coat is often tition and foragers, as well as differences in moisture, har d and impermeable to saltwater. Even so, many of temperature and soil conditions, to sprout and survive. these drifters become waterlogged and sink before they reach land. The Gulf Stream current, flowing north from The South Atlantic equatorial current, feeding into the South America and the Gulf of Mexico, deposits Gulf Stream, carries seeds and fruits from Africa, including many sea beans on eastern Florida beaches. the sea heart, true sea-bean, sea purse and gray nickernut. All sea beans shown at actual sizes True sea-bean or hamburger bean Sea-coconut Mucuna spp. Manicaria saccifera Mary’s bean Produced on vines, these Also known as a sleeve palm, this Merremia discoidesperma This seed carries the dis- seeds break out of pods species is native to the American tinctive mark of a cross on that have tiny stinging tropics. The fruit may contain one, one side. Some think the hairs (not visible here) two or three seeds and the species cross gives the seed special to discourage preda- may be har d to identify depending meaning and protection to the tors. In Africa, this sea on which layer of the fruit or seed owner. In some cultures, these bean is carried as a is exposed. This sample shows a seeds were passed down from mother to daugh- charm to prevent single seed with a partial fruit coat. ter to be squeezed during labor to ease delivery. illness. The seeds The seed comes from a woody vine that grows may remain in Guatemala, Chiapas, Mexico and Hispaniola. buoyant for one Fruit coat Seed Although the seeds may be viable when washed to two years ashore, seedlings in Florida usually are eaten and are among by insects, preventing the vine from spreading. the most com- Gray nickernut monly found Caesalpinia bonduc This species, native to southeast Asia, sea beans. can be found throughout the Caribbean and in South Florida. It Bay bean grows as a spiny shrub, forming Canavalia rosea dense thickets just above the high This species forms a thick tide zone. The prickly pod houses tangled vine on beaches seeds which are sometimes used throughout the tropics. The as marbles (nicker is another name seeds can drift and remain for marble). The seeds are also used Seed Pod waterproof for up to a year Pod as buttons, jewelry and in various rem- and a half, and most are still edies for controlling fevers and dysentery. Seed viable when they wash ashore. They may drift for more than two years, with most of the seeds remaining viable. Tropical almond Terminalia catappa Crabwood Jamaican naval spurge Carapa guianensis This is one of the most Omphalea diandra common tropical drift This species is a native These seeds wer e originally packed inside an tree of western hemi- fruits. Originally from orange-sized hard-shelled fruit that comes from tropical Asia, this spe- sphere tropics, including a climbing shrub found along beaches, tidal South America and cies is grown for its swamps and rivers in the tropics of the edible seeds, which taste Guyana. The seed may Americas. As the fruit breaks open, the seeds drift for one to two years like almonds, and as an are released and drift to the ocean. Unbroken excellent shade tree. The outer with about half remaining seeds may float for two years, and half of these viable. covering is soft and corky, en- may still be viable when they wash up on the beach. abling it to remain buoyant at least two years. Half of the seeds that wash ashore may be viable. Sea purse Dioclea reflexa Coin plant Drifting from Asia, these seeds have reached Dalbergia ecastaphyllum Blisterpod shorelines throughout the tropics and successfully This species occurs as trees, Sacoglottis amazonica colonized those areas. Some seeds have washed shrubs or vines found in man- Native to the South American grove swamps in the tropics of Amazon and Orinoco River basins, ashore as far away as northern Europe by traveling with the Gulf Stream. the Americas. The wood from these small trees produce unusually this species, known as rosewood, lumpy seed coverings. They may has many uses. Roughly 25 percent can remain viable drift for two years and about 30 after a nine-month trip. percent of the fruits contain a viable Black pearl seed. Although the seeds often wash Sapindus saponaria up along the shores of Jamaica and other Caribbean These trees are native to the American tropics. The islands, they have not been successful there. Sea heart seeds resemble black pearls and often are used to Entada gigas make necklaces. Crushed seeds have been used as Found in the Amazon, fish poison and the fruit has been used as an astringent. the Caribbean, Cuba Anchovy-pear The seeds may remain buoyant for 14 months, and seeds and Hispaniola, this that wash up on Florida beaches from Cuba usually are viable. Grias cauliflora woody tropical vine Native to the produces long fruits American tropics, with up to 15 individual this tree grows along Screwpine compartments holding rivers or in marsh Pandanus spp. seeds like this one. Most forests. The seed Not pines at all, these eastern hemisphere tropical plants of the seeds remain viable pods travel by river to have palmlike stems and bear an edible fruit resembling for the two years they may the sea, where they a pineapple. The roots and leaves are used for making drift before washing ashore. may drift for one to two ropes, baskets, mats and hats. The screwpine now is Considered luck charms by many collectors, the years. By the time they cultivated in southern Florida. seeds ar e often polished and engraved with artwork. wash ashore, many are dead or dying; only about 10 percent survive the journey. Manchineel Cocoid palm Hippomane mancinella Orbignya cohune This seed comes from trees that form These trees are natives of the Atlantic coast dense thickets along tropical shorelines Starnut palm from southern Mexico to Central America. throughout the Caribbean and along the Astrocaryum spp. The leaves of the mature tree may be up to coasts of Central America and northern This species is native to tropical 60 feet long and 6 feet wide. The seed, typical South America. Parts of this tree are very America and the West Indies. The of palms, has three pores on one end that poisonous and the milky juice found in the fruits will blister husks that wash up on our beaches resemble a face. It may remain adrift for more skin. The drift seeds, which are harmless, may remain buoyant may have been drifting for two years than a year but usually lacks any viable seeds. for up to two years with a 50 percent chance of viability. and usually lack a seed. Finding sea beans Growing sea beans Antidote vine Fevillea cordifolia When looking for sea beans, search the line of To try to grow a sea bean, make a small slice This high-climbing woody vine is found in fresh water seaweed marking the normal high tide line. Also into the seed coat to allow fresh water to enter. swamps in the tropics of the Americas. The seeds search the line of seaweed higher up the beach, Soak the seed in fresh water for 24 hours. Then may drift for up to two years and remain viable if wher e storm tides deposit material. Clean the plant it in potting soil to a depth of 1 or 2 inches. undamaged. Seeds which germinate in fresh water seeds with soapy water or alcohol to remove oil Seedlings of the sea heart, true sea-beans and will die when they reach the ocean, as they cannot and dirt. Seeds with hard coats can be polished the sea purse will emerge in about four weeks tolerate salt water. using fine sandpaper or in a rock tumbler. if the seeds are viable. SOURCES: Mary Barnett, Nova Center for Applied Research and Professional Development; Dr. Dan Austin, Florida Atlantic University; World Guide to Tropical Drift Seeds and TINA GWALTNEY/Research Fruits by Charles R. Gunn and John V. Dennis; Grolier Multimedia Encyclopedia; Ocean Journeys by Mangrove Seedlings by Charles R. Gunn and John V. Dennis. JIM WEBB/Staff graphic.