How slow plants make ridiculous seeds

Coco de mer palms go extravagant on a tight budget

man holding coco-de-mer nut

HUGE SEEDS  The iconic shape of a coco-de-mer nut that intrigues a traveler (shown) won’t show up on a tree. It’s evident only once the outer green husk is stripped off.

Niall Corbet

The secret behind the world’s largest seed and its sexually extravagant plant is good gutters.

A prodigy among those seeds can weigh as much as 18 kilograms, about the weight of a 4-year-old boy. Yet the plant that outdoes the rest of the botanical world in the heft of its seed manages with below-poverty nutrition. Coco-de-mer palms (Lodoicea maldivica) are native to two islands in the Seychelles that have starved, rocky soil.

Despite the scarcity of resources, a palm forest is “magnificent — it’s like a dinosaur could come around the corner,” says Christopher Kaiser-Bunbury of the Seychelles Islands Foundation. Wind jostling acres of stiff leaves makes a sound he describes as “crackling.”

coco de mer leaves
An adult coco-de-mer’s leaves collect water from a 17.1-square-meter area on average. C. Kaiser-Bunbury
But it’s scrimp-and-save greenery. With precious little nitrogen and phosphorus (the N and P in N-P-K garden fertilizers), these palms sprout fronds using only about one-third of the nutrients in the leaves of 56 neighbor tree and shrub species. And the trees scavenge fiercely from their own dying leaves, Kaiser-Bunbury and his colleagues report in the May New Phytologist . Coco-de-mer palms can reuse 90 percent of that prized phosphorus from fronds about to drop, leaving the most depleted dead leaves yet recorded.

Sexual structures, however, are luxuriant, taking about 85 percent of the plants’ supplies of phosphorus. And the palms manage this, the researchers conclude, thanks to drainage. Curving leaves, easily 2 meters wide with creases like folded paper fans, coil almost like funnels to send rain sluicing down the stems. The water deposits its treasures of animal droppings, stray pollen and other nutrient windfalls over the roots.

A plant’s giant seed takes time to grow — six years — especially on a tight nutrient budget. A wild coco-de-mer lives slowly, reaching 80 or 100 years of age before plant puberty. During a female plant’s life of several hundred years, she may bear only about 100 seeds.

Unfortunately, the coconuts produced with such sustained effort rarely get a chance to replenish the dwindling forest. To sustain the forest, Kaiser-Bunbury calculates, 20 to 30 percent of the endangered species’ seeds need to sprout. But perhaps inevitably, considering all the showy reproduction, poachers sell powders made from the coconut’s insides as alleged aphrodisiacs. 

Susan Milius is the life sciences writer, covering organismal biology and evolution, and has a special passion for plants, fungi and invertebrates. She studied biology and English literature.

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