Apples and strawberries, or how pollinators feed us

You may have heard that pollinators are suffering and that we need to support them so they can continue to stay around us. You may also have heard that as humans, we need pollinators because if we lose them, we also will lose our ability to feed ourselves. How is this so? In this blog post, I want to take some time to think about the importance of this, visiting two examples of foods very familiar to us: apples and strawberries. Hopefully, by the end of this article, you will be sending loving thoughts to pollinators every time you take a bite of these delicious fruits. 😊

Do apple trees need pollinators?

Like for all fruits, apples form after the fertilization of the ovules present in the apple flowers (check out this blog about how this works). If pollination and then fertilization happens, we end up with juicy and large fruits, which enclose the plant’s seeds, and which can be used by the plant to disperse their seeds. For this reason, the fruit we eat will only form if there has been fertilization. Unlike other plants which can use their own pollen to form fruits, apple flowers (but also cherries, apricots, and peaches) cannot do so, and they need to have an organism actively transfer the pollen from one flower to another: a pollinator!

Pollinators of apple trees can be of many types but they are mostly bees. These insects are sometimes managed, with a large series of honeybee or mason bee colonies brought to orchards or gardens to support pollination. Many times, however, it is not the showy presence of these large managed colonies, but the quiet “hidden” activity of a multitude of solitary and wild bees who perform the pollination of these flowers. (Read here to learn about wild bees.) These pollinators are often overlooked, but it is really these little ones that save the day in most gardens.

Apple flowers are pollinated mostly by bees, which can be managed (like honeybees), or wild (like metallic bees or native bumblebees). Photo: Hugo.

Sometimes we don’t realize the value of something until we don’t have it anymore. If you have apple trees in your garden or on your farm, you may have realized that if we have a year with a cold spell when apple trees are flowering, the tree will produce very few apples. This is most times directly related to the need for pollinators that these plants have. In fact, insect pollinators have trouble moving and flying at cold temperatures, which means that if it gets cold when the apple tree flowers, pollinators will not be able to visit the flowers because they cannot reach them. If the spell lasts throughout the whole flowering time, then most of the flowers will not receive any pollen and no fruits will be formed.

Weirdly-shaped strawberries? What’s going on?

The region where I grew up in Argentina is locally known for their delicious strawberries. Every early summer, we would get these small wooden boxes with small, sweet, and incredible strawberries. We would then wash and cut them, and eventually eat them like that or (my favorite) with whipped cream. I never thought at the time that I would today be thankful to all those pollinators for creating such fond memories I can keep forever. How so?

As most plants, strawberries can partially self-pollinate, but get better pollinated if pollinators are around. Like apples, strawberries flower early in the growing season, and a cold spell during their blooming time can make them lose their pollinators, and can lead to irregular strawberries or to no fruits at all. Why is this?

Strawberry flowers are formed by a multitude of mini female organs (shown with the black arrows, on the left), which eventually become a multitude of mini-fruits (shown with the white arrows on the right). Each of these mini-fruits carries one seed and is held by a “base tissue.” The group of all these mini-fruits and the base tissue is what we call a strawberry. Photo: A. Espíndola.

In the case of strawberries, what we consider a fruit is in fact a series of tiny fruits (each little seed we see on a strawberry is one of those fruits) all growing together and in parallel on a “base tissue.” It is this whole “mega-fruit” that we call a strawberry and that we eat. As for apples, strawberries are also particularly well-pollinated by bees, and it has been shown that it is really the wild bees that we need to thank for their services here! Also, like for apples, when pollinators are not around because they are just not able to survive in the area or because they can’t move due to low temperatures, only some of these tiny fruits will get to receive pollen and be fertilized, meaning that only those parts of the “mega-fruit” will get to develop. When this happens, we obtain strawberries that are odd-shaped and that look deformed. These strawberries can still be eaten; they are just not as full and sweet as they could have been if the pollinators had been around.

I want apples and strawberries. What can I do?

We have treated in previous blogs some specific actions you can take in your own green spaces, gardens, and orchards to help pollinators thrive and continue helping us get our own delicious food. And in fact, what better way to thank them for their help in feeding us than to provide food and nesting spaces for them!

By Anahí Espíndola, Assistant Professor, Department of Entomology, University of Maryland, College Park. See more posts by Anahí.

Anahí also writes an Extension Blog in Spanish! Check it out here, extensionesp.umd.edu, and please share and spread the word to your Spanish-speaking friends and colleagues in Maryland. ¡Bienvenidos a Extensión en Español!

2 Comments on “Apples and strawberries, or how pollinators feed us

  1. I learned a lot from reading your article about flower pollination. Thank you for writing this article with a lot of patience for the reader. Many more like me will learn a lot about flower pollination by reading your article. Thanks again.

    Like

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