The secret behind the world’s largest seed is leaves that serve as good gutters. During rains, they channel lots of water and nutrients right to the plant’s thirsty roots.
Coco-de-mer palms (Lodoicea maldivica) produce these monster nuts, which are a type of seed. The biggest can tip the scales at up to 18 kilograms (roughly 40 pounds). That’s about as much as a 4-year-old boy. Yet the palm outperforms all other plants — at least in seed heft — with a below-poverty diet. These plants grow wild on nutrient-starved, rocky soil on just two islands in the Seychelles. (They’re part of an arc of some 115 islands in the Indian Ocean, off of the East Coast of Africa.)
Christopher Kaiser-Bunbury works for the Seychelles Islands Foundation. Despite a scarcity of nutrients to fuel its growth, a palm forest is “magnificent — it’s like a dinosaur could come around the corner,” he says. Winds can jostle hectares (acres) of stiff leaves. This makes a sound he describes as “crackling.”
Nitrogen and phosphorus are two natural fertilizers — nutrients — that these (and other plants) need. There isn’t much of either on the islands where these palms grow. So the plants are frugal. They sprout fronds using only about one-third the nutrients needed by leaves of 56 neighboring species of trees and shrubs. What’s more, coco-de-mer palms scavenge a lot of the nutrients shed in their own dying leaves. These trees can reuse 90 percent of that prized phosphorus from the fronds it’s about to drop. That’s a record for the plant world, report Kaiser-Bunbury and his colleagues in the May New Phytologist.
Creating its monster seeds uses up about 85 percent of this plant’s supplies of phosphorus, the biologists estimate. And the palms manage this, the researchers conclude, thanks to drainage. The palm’s curving leaves easily can span 2 meters (6.6 feet). Creases in them make the leaves resemble folded paper fans. Any rains falling on them will funnel down the stems. That water washes animal droppings, stray pollen and other materials — a nutrient windfall — off of the palm and onto its hungry roots.
Each giant seed takes a long time to grow, about six years. But that won’t happen until the palm first reaches plant “puberty.” On the nutrient-poor ground, this reproductive coming-of-age may take 80 to 100 years. Only then can one of these palms yield its first seed. Throughout a female coco-de-mer palm’s life of several hundred years, it may bear only about 100 seeds.
Few of those monster coconuts will get a chance to replenish the dwindling coco-de-mer forests, however. Kaiser-Bunbury calculates that 20 to 30 percent of the endangered species’ seeds must sprout to keep the forests growing and healthy. But that hasn’t been happening. Nut poachers have been illegally kidnapping the seeds. Then they grind them into a powder that they sell.