The buzz in your seasonal latte: Who pollinates the pumpkin spices?

Wow, fall is here. When did that happen?! And because this fall comes after a tortuous year, I want to spend time doing some soul pampering. It is for this reason that, until the end of the year, I will be talking about many of the yummy foods we love and that many times help us through rough times. And to start the series, and matching the fall season, let’s talk about how the spices that create “pumpkin spice” – cinnamon, nutmeg, ginger, cloves – go around getting pollinated and reproduced.

pumpkin spice products

How do you know it’s the fall in the US? We’re surrounded by pumpkin-spice
everything! Photos: PatentingPatch, M. Mozart, J. Kramer, theimpulsiveguy.

As a general introduction to these spices, we have to realize that they all originate outside of the US, and that most of them are even today not produced in the US. This is important to mention because it is humbling to realize how much our food habits (especially those related to comfort foods) are based on foods that are imported by the US. Further, even if that may seem futile, markets for these spices have been historically and are still currently huge, with power over these markets driving major geopolitical clashes, setting the foundations of the current global distribution of wealth, and sustaining (and sometimes undermining) societies around the world.

cinnamon

The cinnamon bark is collected by “peeling” the tree (Photo: P. Nijenhuis). Cinnamon flowers are pollinated by many insects, but several Apis species are particularly important (Photo: D. Valke). Shown are Apis cerana and Apis dorsata visiting other flowers (Photos: Peterwchen, R. Thumboor).

Cinnamon

The cinnamon we eat comes from the bark of cinnamon trees. This bark is either ground or consumed in strips, which are added to savory and sweet foods. Cinnamon trees originate in South Asia and are adapted to growing in wet tropical forests. Today, the most important cinnamon producer is Sri Lanka, and most of the exports go to the USA and Western Europe. Even though we do not eat the fruits of this plant, pollinators play a key role in their reproduction. Cinnamon flowers are poor “selfers,” meaning that they produce the most seeds if receiving pollen from a different flower. These flowers thus rely on insect pollinators for their reproduction (see this post for more details about how flowers function) and among the most abundant species are three Asian “cousin” species of the managed honeybee, as well as some flies.

Nutmeg

Nutmegs are the seeds found in the fleshy fruits of the nutmeg tree (Photo: B. Vauchelle). Nutmeg flowers are very small, pollinated mostly by thrips, and through a deceit-based pollination called “mistake pollination.” (Photos from Sharma and Armstrong, 2013). White bars indicate 1mm.

Nutmeg

The nutmeg we consume is the seed of the fragrant nutmeg tree, which originates in Indonesia. Even though currently it is cultivated heavily in Indonesia and Malaysia, it is also produced in the Caribbean. Because the food we consume is part of the fruit of this tree (there is no nut if there is no fruit), pollination of this crop is central for food production — and this is a super-fun crop to learn about!

Indeed, only some nutmeg trees bear fruit, because half of the seeds of this plant produces male trees (which produce pollen) and the other half produces female trees (which will make fruits and nutmegs). The fun pollination story doesn’t end there, though. The flowers of these plants are tiny, bloom in the night, and need pollinators to transport the pollen from the male trees to the female flowers. So who does this job? A lot of insects! Studies in the species have demonstrated that most pollination is done by tiny thrips, and probably also some beetles, flies, and maybe some bees (here you can read about pollinators other than bees).

But let’s spice up (pun intended) this story! This plant is not only pollinated by uncommon types of pollinators; it also tricks them into pollinating! In fact, the insects are interested only in male flowers, where they can collect pollen they can feed on, and they do not care about visiting female flowers, which do not offer any pollen or nectar. Thus, the strategy used by female flowers to attract pollinators is to trick them by making them assume they are actually male flowers, a strategy known as “mistake pollination”. It’s only after they entered the female flower and deposited pollen on the stigma that the insects realize their mistake.

ginger plants

Ginger plants grow from the rhizomes we consume and production is based on clonal reproduction (Photo: S. Podhuvan). Flowers are showy and small, but their pollinators are not well known (Photo: Ogniw).

Ginger

The part of the plant we consume from ginger is its rhizome, meaning that one can plant the piece of ginger one buys in the store and one would grow a ginger plant! This plant species also originated from the Southeast Asian archipelago. The plant is easy to grow, and thrives in warm climates, but most of the world production is currently from India. Under production conditions, ginger is multiplied through the planting of rhizomes, meaning that most of the production is not based on seeds. For this reason, the pollination of this species was not of high production interest until only recently. Indeed, while ginger propagation is based on rhizomes, this does not allow for the use of sexual reproduction for the development of better new varieties that may be resistant to diseases or pests. Recent studies indicated that ginger is extremely hard to pollinate because pollen has a low rate of successful pollination, leading to very low seed success. Several researchers are now focusing on identifying its pollinators, so stay tuned to know more!

cloves

Cloves are the dried immature flowers of the Clove tree. Flowers are harvested right before they open and are dried to reach the product we find in our markets (Photos: Midori, A. Heijne, Peripitus).

Cloves

As with most other spice plants treated here, cloves also come from a tree, which originates from the Moluccas, in Indonesia. While the plant originates in those islands, most of clove production is currently from Indonesia and Madagascar. The part of the plant consumed is the flower buds, which are harvested and then dried to produce the spice we buy. Although we consume the flowers, these plants still require seed production to reproduce, and this is central to maintaining clove production. Because the plant can self-pollinate but its genetics are improved by cross-pollination, pollinators are very important for its reproduction. Here, again, pollination is not very well known, but flies, bees, and some butterflies are suspected to play an important role in transferring pollen, as it has been observed in a closely related (but not cultivated) species.

Note: this blog post is dedicated with love to Luke Harmon, who despises Pumpkin Spice. ❤

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

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