Onion and its layers

The dried stem and the dried outer layers (left). A section of the onion where the centre bulb is surrounded by layers (right). A shallot (centre) with the dried stem and basal disc at bottom.

With its many layers, life is like an onion. Each person is like an onion.

But have you ever wondered why is an onion like an onion? Why does it have so many layers?

Surprise, surprise! The onion layers are in fact modified leaves.

As the onion plant grows, part of its leaves, surrounding the bulb, begins accumulating nutrients for the bulb and becomes fleshy. Depending on the availability of nutrients and water, the layers can increase in number to provide the needed nourishment. As nutrients from the outer layers are used up, they lose their cell form and dry up.

As the harvesting time approaches, the outer leaves become papery but continue to protect the onion bulb from physical damage as well pests and fungal rot. It is this dried up leaf layers that we peel away before cutting an onion.

Sources and further reading:

1. Onion Description (https://en.wikipedia.org/wiki/Onion#Description).

2. Onion trivia (https://www.onions-usa.org/all-about-onions/trivia/).