Because there are more than 3,000 species of palm in the world, identifying one by its seed may seem daunting at first. Many varieties of palm seeds float great distances, finally beaching on shores many miles from where they originated. These drifting seeds are commonly called "sea beans" until the tropical plant they came from is identified. If you come across one during a morning stroll on the beach, pick it up and look for clues to its identification from its appearance.
Collect palm seeds on the beach at low tide. Many will be tangled up in clumps of seaweed and other debris, and some will still be encased in their seed coats. Coconut palm seed is easy to identify because of the familiar shape of its seed coat, the coconut. It has a hard, hairy shell between the size of a softball and a volleyball. Cohune palm seeds are about the size of a chicken egg and are usually rough at both ends due to drift and water damage. Nypa palms look like an arrowhead with a bristly point.
Look at the color and shape of the seed. Coconut seeds are deep, reddish purple, about the size and shape of a plum. The hard seeds of Sabal palms are tiny and round by comparison, black or rusty colored. Ivory palm seeds have a smooth, tan surface and an oval shape. Maripa palms, which are quite rare, have a seed that looks like a spindle, about 2 inches long. Observe textures on palm seeds, but don't rely on them to identify the species. Depending on how long a palm seed has drifted, it may be smooth and polished, or rough -- much like beach glass.
Find specific markings on the seeds. Starnut palm has three distinct pores at the bottom of the seed, where the palm will eventually sprout. Each pore is surrounded by light-colored striations that resemble stars. African oil palms have similar pores and striations, but the lines do not form stars. Nypa palms seeds have long, linear markings that appear as the seed dries and cracks.
Plant the seed in a sandy, sunny location. Mark it with a stake to help you remember where it is because it may take months to germinate. If it sprouts, you will be able to identify it readily from the leaf with the help of a field guide for tropical plants.