How Does Water Get Inside Of A Coconut?

A cluster of coconuts growing on a coconut tree.

Water seeping into coconuts isn't something most people think about on a daily basis, but it's something that has been happening in nature for hundreds and hundreds of years. Coconuts are made by coconut palm trees, and the water that you can find in coconuts doesn't just magically appear. It's a byproduct of the way the trees interact with the world around them to draw water from the ground and transport it up to the fruits.

The process starts with the coconut palm’s roots. These roots are buried deep in the soil, and if it weren’t for them, trees wouldn’t be able to collect water. The roots branch out and are long and deep enough to reach underground water. The soil that the coconut trees use contain both rainwater and water that has seeped in from nearby sources like rivers, and the roots are built and structured in a way to suck it all up. Don’t think that the tree just uses a big straw to suck it up, however, because it’s a little more complicated than that! The water, instead, moves into the roots through something called osmosis. Osmosis is the movement of water from an area of excess water to an area with less water across a barrier/wall, which allows small objects to pass through but not big objects. In this case, the root cells have less water inside them compared to the wet soil outside, and thus, water flows into the roots in an attempt to level things out. This is the first step of getting water from the ground to go up to the coconuts.

Once the water is in the roots, it doesn’t just sit there. The coconut tree moves it up through the trunk and out to the leaves and fruit. This is successfully done by the tree with the help of various scientific concepts working together. One example of such a scientific concept is capillary action. Capillary action is when water travels up tight spaces, like little tubes, with no help. In the tree, there are narrow channels called xylem that work kind of like those tubes. Water sticks to xylem walls and is pulled up as it tries to stay together. The xylem runs from the roots to the top of the tree, so it's almost like a water highway. It's not fast, but it's steady, and it keeps going as long as the tree's alive and the soil has water to give.

Transpiration is another thing that helps water go up, and it’s related to how the tree “breathes.” Transpiration is the process by which water evaporates from leaves into the air. Coconut trees have big, flat leaves with extremely tiny holes known as stomata, and water is changed to vapor and drains out of the holes. When water exits the leaves, it creates a pull that draws more water up from below. In a way, it’s like a chain reaction; the water is sucked up by the roots, pumped by the xylem to the top, and expelled out through the leaves, circulating the whole system. This transpirational traction is strong enough to pull water dozens of feet high, right to the top of a tall palm tree.

The water is now coming up the tree, but how do the coconuts get so much water on the inside? Coconuts do not form water within themselves. They start as flowers on the tree and become small green fruits after being pollinated. Over time, as the coconut continues to grow, they receive water and nutrients from the tree via a tissue system. The xylem we mentioned earlier does not stop at the leaves. It bifurcates and reaches into the growing fruit. Water comes into the coconut via these channels and fills a hollow cavity inside. This cavity is lined with a layer of tissue called the endosperm, which initially comes in as a liquid. That liquid is the coconut water, and it builds up as the fruit matures.

The coconut water isn't really pure water from the ground though. During the transporting process, the tree adds things to it. As water moves through the xylem, it picks up minerals like potassium and magnesium dissolved in the soil and plant tissues. The tree also generates sugars and other nutrients in the leaves through photosynthesis, and some of that is funneled into the coconuts and their water as well. As a result, coconut water is actually a mixture of water, minerals, and sugars that the tree assembles. This is why coconut water has some nutritional value and tastes different than just regular tap water.

The volume of water in a coconut differs depending on how mature the fruit is. Coconuts are immature and green when they contain a great deal of water inside, at times even up to a pint or more. During this time, the endosperm is still primarily a liquid. As the coconut matures, the liquid endosperm hardens and eventually becomes that white solid material that we can eat, and the water content reduces. The tree still supplies water to the fruit, but the coconut uses it to build the solid endosperm instead of keeping it liquid. Once the coconut is brown and ripe, there is only a trace of water left, and the inside is largely made up of just a thick, edible layer.

Weather and earth play a major role in the quantity of water that enters coconuts too. Coconut palms prefer hot, moist places like tropical coastlines. If there is a drought, the tree will struggle to pull enough water, and the coconuts will contain less liquid. Soil type matters as well. Sandy soil, which is near coastlines, drains rapidly but holds enough water for roots to use, while clay soil, although it holds more water, is more difficult for the roots to penetrate.

The whole system goes together neatly if you think about it. Water enters the roots through osmosis, travels up the xylem with help from capillary action and transpiration, and reaches the coconuts as they grow. Minerals and sugars are deposited on the way by the tree, which is what makes the coconut water that we drink so tasty and nutritious. It's a slow, consistent process that keeps going as long as the tree is alive and the weather is favorable.