At first glance, you might think that strawberries are a type of fruit with seeds, but in reality, that’s not the case.
Strawberries are a favorite fruit for many, not only because of their flavor but also due to their unique appearance. They are bright red when ripe, particularly featuring ‘seeds’ on the outside. But why are these “seeds” on the outside, while the seeds of many other fruits—such as apples, oranges, kiwis, and mangoes—are inside?
Aaron Liston, a professor and director of the herbarium at the Department of Botany and Plant Pathology at Oregon State University, explains that this is actually a puzzling question. “What looks like the ‘seeds’ of strawberries are actually the fruit themselves,” he states.
To begin with, fruit develops from flowers. A flower consists of: ovary, ovules, petals, sepals, stamens… Most of these are attached to a part called the receptacle.
Strawberries.
Typically, after fertilization, the ovules will turn into seeds, and the ovary will thicken to form the fruit. The remaining parts of the flower will fall off.
However, strawberry flowers have many ovaries. When fertilization occurs, these ovaries produce numerous small fruits (true fruits), but instead of swelling, the receptacle thickens to form the red, fleshy part we eat (false fruit).
The true fruits attach to the surface of the false fruit. The remaining parts of the flower will fall off. Thus, the small seeds we see on the outside of strawberries are actually their true fruits. Inside each true fruit is a seed.
Very few types of fruit have evolved like strawberries (genus Fragaria), but a distant relative known as mock strawberry (Duchesnea indica) looks exactly the same. Both share a common ancestor from about 20 million years ago, so it’s likely they evolved independently to resemble each other through a process called convergent evolution, Liston explains. However, mock strawberries are not as sweet. “They taste like cardboard,” he adds.
Meanwhile, strawberries do not solely rely on seeds to grow new plants. If conditions are poor and the strawberry plant cannot disperse seeds, it can develop runners or branching stems to start a new plant.
