Garlic, Onions, and Bulb Semantics

I like to know what plant parts I consume–not because I am worried about it, but because it is interesting to me. I bet you know that an onion is a bulb. You may or may not know that a bulb is a modified stem and not a root. But that is not what led to this post. I was asked some questions about garlic recently that I could not answer, so it led to an investigation.

Are garlic and onion the same structure?

I know the textbook answer is that garlic is a bulb just like an onion. Onions have distinct layers, which are modified leaves wrapped around a modified stem.

Onions have layers (note green modified stem in the center).

Garlic does not have these distinct layers when sliced. To use culinary terminology, there are cloves arranged in a head. So is each clove a modified leaf and the entire structure a bulb, or is each clove a separate bulb?

One bulb or many?

After doing some reading and reasoning my understanding is that each clove of garlic is a separate bulb. While distinctive layers are often lacking in an individual clove, it is comprised of a modified stem (which is normally green, though it might be very reduced) and a modified leaf that surrounds it. Since each clove arises from a bud and contains a modified shoot it is considered a bulb. So a head of garlic contains many cloves, each of which is a bulb.

A garlic bulb sliced open, revealing the modified stem.

I use garlic very sparingly. In fact, when I buy a head of garlic I often use two or three cloves and the rest of the head ends up drying out before it gets used.

Now you’re prepared for a discussion on the anatomy of garlic and onions.


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