Why do coconuts have water?

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📓 The short answer

Coconuts carry water because they’re designed to launch a seed with an immediately usable food reserve. This liquid endosperm supports early growth, while the meat provides sustained fuel as the seedling develops.

📚 The long answer

Coconuts are an unusual fruit (yes, they are a fruit, not a nut).

If you cut open an orange or a mango or a blueberry, there's lots of water embedded in the fruit flesh. But you crack open a coconut, stick a straw in, and it's like a juice box.

Coconuts fall into the fruity category of drupes, or stone fruit. Other drupes include apricots, olives, mangoes, cherries, and amlas. A coconut, like other drupes, has three layers:

1. Exocarp: The outer skin.
2. Mesocarp: The fibrous husk.
3. Endocarp: The hard interior shell that protects the seed (which contains the embryo).

Within the endocarp you'll find coconut water and coconut meat, liquid and solid endosperm that feed the embryo during germination. About two months after flowering, the endocarp starts to accumulate coconut water.

The water is drawn up from the ground by the palm's extensive root system (1-5 meters deep), along with the nutrients of the soil. It travels up the trunk, through the branches, and finally into the baby coconut. This liquid is highly nutritious and supports the growth of the embryo. At around six to eight months, a young coconut is full of water, up to 1 liter.

But water is not the only thing you'll find in a coconut's cavity. As the coconut matures over the course of a year, most (but not all) of the liquid endosperm solidifies into the white, fatty kernel called coconut meat.

Many other plants (like wheat or corn) develop fully solid endosperms. But not the coconut: even mature ones remain partially filled with coconut water.

So back to the original question: Why do coconuts have water?

Reason #1: Coconut water is rich in nutrients and easily accessible during germination

Coconut water is truly a growth serum. It's full of vitamins, minerals, amino acids, sugars, and plant hormones that stimulate cell division (cytokinins). In fact, some studies have found that formulated coconut water is comparable to commercial, synthetic fertilizers.

This liquid gold is critical in the coconut's germination phase, when the embryo develops into a seedling. During this process, coconut seedlings develop a haustorium, or sponge-like absorbent orb, that uses up both the coconut water and meat over time.

If there is not enough coconut water, the haustorium can't fully expand and the seedling fails to germinate. This liquid endosperm gets absorbed first, likely because it’s immediately available and easier to use than the solid endosperm.

In other words, the seedling relies on both: the quick-access liquid endosperm and the longer-lasting energy stored in the solid endosperm.

Reason #2: Coconut water helps the embryo germinate on sandy beaches.

Unlike other fruits that rely on animals to disperse their seeds, coconuts spread along coastlines mainly by floating in sea water for long stretches. A wild coconut can remain viable for germination for ~110 days in the ocean, floating for up to 3,000 mi (4,800 km). We actually don't know exactly where coconuts originate from because they have been embarking on ocean voyages for thousands of years.

Coconuts have evolved specific traits to help them survive these extensive sea voyages and later germinate on sandy beaches. For example, they are buoyant because of their fibrous husk, nearly empty cavity, and waterproof exterior.

When they finally land on a beach, the reserve of coconut water gives them a better shot at surviving before its root system is deep enough to reach fresh water and its leaves are able to push out of the shell and into the sunlight.

--- Thanks for reading this week's newsletter! If you have any thoughts, questions, or favorite GIFs, my inbox is always open. Just hit reply to send me a note! :) ​ All my best, Caitlin ​Click here to read five facts about Caitlin​

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​Sources for this week's newsletter​

🌐 Wikipedia article of the week

​Salad oil scandal​

"The salad oil scandal, also referred to as the soybean scandal, was an American major corporate scandal in 1963 that caused over $180 million ($1.89 billion today) in losses to corporations...
​
The scandal involved the Allied Crude Vegetable Oil company... Ships supposedly full of salad oil for Allied would dock, and inspectors would certify the cargo, allowing Allied to post the oil as collateral and obtain millions of dollars in bank loans. In reality, the ships tanks contained only water, with a few feet of salad oil floating on top to trick inspectors."

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👀 Catch up on other curious questions

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