A Seed That Sails the Seas

By Awake! writer in Britain

I WAS walking along a sandy beach strewn with seaweed and driftwood on England’s east coast when an unusual pebble caught my eye. I picked it up. It was smooth and chestnut brown​—but this was not a pebble! What was it? A tropical drift seed, commonly called a sea bean. How did it get there?

Sea Bean Origins

This bean is, in fact, a seed produced by a giant legume, called a liana. The Concise Oxford Dictionary defines “liana” as “a woody climbing plant that hangs from trees, especially in tropical rainforests.” It uses its tendrils to climb up its host tree​—sometimes as high as 100 feet [30 m] above the forest floor. This plant is widely distributed along coasts and rivers in central and western Africa, Colombia, the West Indies, and Central America. In Costa Rica, where arboreal monkeys use it to travel from treetop to treetop, it is known as the monkey ladder.

Measuring up to two and a half inches [6 cm] across, the seed starts its life in a huge pod hanging from its support tree. This large seedpod can grow up to six feet [2 m] in length. It is made up of rounded segments containing one seed each. These are separated by a thin groove. As with many common beans, when the seedpod first forms, it is soft and green. But as it ripens, the pod hardens, becoming dry and heavy. It also turns brown and begins to look woody.

Eventually, because of its increased weight, the seedpod drops off into the river or sea. As the pod floats away, its individual sections break off. Now each seed with its protective casing starts its own journey. Some seeds may get bogged down and grow in the mud along a riverbank. Many, however, will float downriver, sometimes traveling hundreds of miles to an estuary. If a seed journeys through groups of islands, a tide may catch it and wash it onto a nearby beach.

A World Traveler

What happens to a seed that ventures out to sea? Its protective casing gradually wears  away, and the seed falls out. Does it then sink? No, because it is impervious to water. It gets its buoyancy from an internal air cavity caused by the shrinkage of the cotyledon, an embryonic leaf inside the seed. With such a marvelous survival package, this seed, or sea heart​—as it is sometimes called on account of its unusual heart shape—​can travel unharmed in the sea for months, even years, before being cast onto a distant beach.

How does the seed manage to reach such faraway places as the British Isles, Scandinavia, and other parts of Western Europe? For centuries these seeds have been using the Gulf Stream to hitch a ride across the Atlantic. In fact, millions of these seeds are constantly sailing the ocean currents around our globe!

Is our seed still viable after such a long and perilous journey? Well, try nicking its outer coat with a file or a saw, preferably near the hilum, the scar on the seed marking the point of attachment to its seed vessel. Then plant the seed in soil in a pot, water it, and leave it in a warm sunny place. It will likely sprout.

What, though, usually happens to a seed that is washed up onto beaches in the much colder European climates that are not ideal for natural germination? A finder may keep it as a souvenir, but many seeds are collected and sold as novelties, sometimes combined with shells or beads to make attractive necklaces. Those with the best heart shape are highly prized by collectors.

Northern Europeans use sea hearts​—and the more rectangular seed of a closely related species—​to make snuffboxes, matchboxes, and lockets. In England such seeds have been used as teething rings for babies. Sailors often use the seeds as good-luck charms, reasoning that if the seeds could survive such long and perilous journeys across the oceans, they could likewise protect their owners.

So when you next take a walk along a beach, search carefully among the seaweed and driftwood. You too may find a seed that has sailed the seas.

[Picture on page 23]

The hanging pod of the sea bean can grow up to six feet long

[Credit Line]

Courtesy Jean-Jacques Segalen/ Barbadine.com

[Picture on page 23]

Necklaces made with sea beans