Short answer. If the fruit naturally falls onto your land on its own, it belongs to you as the owner of that land. Article 681 provides that fruits naturally falling upon adjacent land belong to the owner of said land. The key word is naturally: you may keep what drops by itself, not fruit you knock or shake down.
What the law says
Fruits naturally falling upon adjacent land belong to the owner of said land.
Civil Code, Article 681 — Fruits Falling On Adjacent Land. Read the full provision →
The land where it lands decides ownership
Article 681 states a simple rule: fruits naturally falling upon adjacent land belong to the owner of said land. Ownership follows the ground the fruit lands on, not the tree it grew on. So when your neighbour's mango or santol drops over the boundary and lands in your yard, it becomes yours, even though the tree and its roots stay firmly on his side. This is an exception to the general idea that the fruits of a tree belong to whoever owns the tree. Once the fruit has left the branch and settled on your soil by itself, the law treats it as belonging to your land.
Naturally falling is the whole point
The rule is limited by one word: naturally. The fruit must drop on its own, through ripeness, wind, or gravity. If it falls to your side without anyone's help, it is yours to keep. What you cannot do is help it along. Climbing the tree, shaking the branches, throwing stones, or using a pole to bring the fruit down is not natural falling; fruit taken that way still belongs to the tree's owner, and doing so may make you answerable for what you took. The law rewards what nature drops onto your land, not what you reach out and harvest.
What the rule does not give you
This rule is narrow, and it is easy to overread. It does not give you any right to fruit still hanging on the tree, even on branches that overhang your property. It does not let you enter your neighbour's land to gather fruit, nor to cut the tree. Other provisions of the Civil Code deal separately with overhanging branches and intruding roots, giving a landowner the right to demand that they be cut, but that is a different remedy from owning fallen fruit. This article speaks only to fruit that has already fallen, and only to who owns it once it lands.
Practical limits and neighbourly disputes
In practice, the rule matters most for trees near a shared boundary, where a good harvest can end up scattered on both sides. The owner of the tree keeps whatever falls back onto his own land, and you keep what settles on yours; the dividing line is simply where each fruit comes to rest. Disputes usually arise not over the odd mango but over who has been shaking the tree or crossing the fence. Because the outcome depends on how the fruit actually came down and where the true boundary runs, the specific facts of your situation control. This is general information, not advice on your particular quarrel.