The scents of flowers

The fragrance of a rose can be irresistibly attractive to many people. But why? A reader’s question about the chemistry of the scents of flowers!

Valerie Moreno: My name is Valine Moreno, I’m from Monterey, California. My question is, “Why do some flowers give off different scents?”

Valine, even though people often stop to sniff roses, lilies, and other fragrant flowers, smells in the plant world exist primarily to attract insects, not us. Over time, different species of flowers have evolved to produce an array of aromas. There are a variety because there are so many different kinds of insects.

Most flower fragrances come from volatile oils. These are in various parts of the plant, like the petals, stamens, or pollen. When these oils evaporate, aromas are released. Temperature and humidity determine when and how intense a flower smells. There are more than 400,000 species of flowering plants — each with its own unique scent. Not all flowers smell good to humans though. Some plants, like the voodoo lily, reek of rotting meat. The nauseating aroma might drive most people out of the greenhouse, but it makes flies and beetles swoon.

Likewise, plants that smell good to us can deter other creatures. Essential oils in cinnamon bark, for example, repel some bugs. Thanks for your question, Valine.

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