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It’s usually easy to know if a vegetable is a vegetable and if a fruit is a fruit. What happens, though, if a vegetable, like an onion, has some characteristics of the fruit. It can be confusing until you unpack exactly what makes an onion a vegetable or a fruit. I mean, is a vegetable like an onion always a vegetable?

An onion is a vegetable because it is an edible part of an herbaceous plant & does not develop from a flower like fruit does. Neither is it part of the reproductive system of a plant, & does not contain seeds– which are other characteristics of fruits.

To answer the question ‘Is onion a vegetable’ means understanding what characteristics an onion has that could make it a vegetable, and how these differ from those of fruits.

Are beans a fruit or vegetable? Check your answer here!

Is onion a vegetable?

Is onion a vegetable?

Onions are vegetables because they are edible parts of herbaceous plants which have no role in the reproduction of the plant & don’t contain seeds. Onions are bulbs that grow underground & are a part of the root system of the plant. They also have to be edible to be classified as vegetables.

A plant is described as being herbaceous if it has a non-woody stem.

The leafy parts of the plant above ground usually die right down in winter, but the parts that are under the ground usually survive.

See the growth stages of onions.

There are herbaceous plants that grow in winter, but their foliage dies back too.

 The roots, leaves, stems, and bulbs are regarded as vegetables if they are edible.

So, we eat the leaves of lettuce and the roots of a potato.

We also eat onions, the bulb of the onion plant, which is a vegetable.

The question of whether a root, tuber, or bulb is a vegetable is not a new one.

I mean beans are definitely part of the vegetable platter.

However, did you know that they are actually a fruit, biologically?

It’s all not quite so straightforward.

Then, of course, we have onions.

Onion is a bulb

To be clear, an onion is a bulb, which is part of a plant that grows under the ground.

It is edible, which qualifies it as being a vegetable.

Onion does not contain seed

Onion does not contain seeds, which means it must be a vegetable.

Then, dietitians recognize onions as forming one of the five portions of vegetables a day we should consume.

This all means that onions are definitely regarded as being vegetables.

Are potatoes vegetables? Find out here.

Is an onion a fruit?

Is an onion a fruit?

An onion is not a fruit, since it is not part of a plant’s reproductive system. A fruit is produced after the flower dies, & is the ovary of the plant. An onion cannot be a fruit because it grows underground and is part of the root system. It does not supply the reproductive cycle & doesn’t contain seeds.

Onions can grow new plant

Onions can grow new plants, which is similar to what fruit does.

This suggests that onion could be a fruit.

However, even though bulbs can contribute to the reproduction of the plant, they do not contain seeds, which are essential to the reproductive system.

This means that an onion is not a fruit.

The function of a fruit is to protect the seed

The function of a fruit is to protect the seeds and play a part in their distribution. They are crucial to the reproductive system of the plant.

If no fertilization takes place, then there can be no fruit and no reproduction.

However, whether the plant is fertilized, the bulb of the plant will still continue to grow and can also produce reproduce themselves.

So, long story short: An onion is NOT a fruit.

See our complete guide on planting onion sets.

Fruit vs. Vegetable

Fruit vs. Vegetable

A vegetable is an edible part of an herbaceous plant & is not linked to the reproduction of the plant. Fruits are a key part of plant reproduction; they are the result of the plant being fertilized and the ovary swelling. Fruit develops around the fertilized seeds.

A vegetable is considered to be part of a herbaceous plant that can be eaten.

These are plants with green, soft stems.

Not all plants are vegetables

Not all plants in this category are vegetables because not all plants are edible.

If we can eat the leaves, stems, roots, or bulbs of a plant, they are vegetables.

There are many species of plants that flower and all of these produce seeds, from which new plants grow.

The seeds of the plant are encased in a fleshy covering that protects it from disease or pests, which is the fruit.

It is also part of the dissemination of the seeds.

As the fruit falls and rots slowly, the seed is exposed and can begin to germinate in the soil below the parent plant.

Fruits are often eaten by animals and humans, who carry them away, and they grow elsewhere.

Fruit is part of the reproductive cycle of a plant, while a vegetable isn’t.

Fruits contain seeds, but vegetables don’t.

Vegetables mistaken for fruits

Vegetables mistaken for fruits

There are quite a few fruits that are mistaken for vegetables, for example: tomatoes, cucumbers, pumpkins, & beans. There are also vegetables that people think are fruits because some are quite sweet and others grow into new plants.

Did you know that pumpkins, tomatoes, and beans are actually fruits, not vegetables?

Of course, pumpkins, tomatoes, and beans contain seeds, which is one of the ways we recognize fruits.

They also grow from flowers.

However, according to the way these fruits are used in cooking, they are treated as being vegetables.

Now think about it from the other side: there are a few vegetables that are mistaken for fruit.

Take the sweet potato, for instance, which is naturally sweet and can be used in desserts, not only as a side dish for a main course.

Then we have potatoes and onions, which help the plant to grow, so we sometimes think that they may be fruits.

It can be very confusing, and sometimes the lines between fruits and vegetables aren’t so clear.

What is a multiple fruit? Find out if strawberries are actually a fruit. 

Is onion a vegetable?


A vegetable is not always quite a vegetable and sometimes what we think is a fruit may just be a vegetable. 

With onions, it becomes easy to work out if they are vegetables. 

They don’t have seeds, do not form from flowers, and are edible. All of this means that an onion is a vegetable.

Greg Volente

Greg Volente holds a Naturalist Certificate from the Morton Arboretum, worked for The Nature Conservancy leading environmental education programs and doing natural areas restoration, and worked in the soil science research & testing lab at Michigan State University. Besides gardening, he's an avid wildflower enthusiast, and loves botanizing, hiking, and backpacking.