The science behind that perfect spring smell

Besides warmer weather, what is your favorite part of spring?

Is it the flowers with all their vibrant colors? 

Maybe it’s the sounds as new bird species arrive. For this writer, the best part of spring might actually be the smells.   

Spring air in the Lowcountry is full of glorious aromas, and the smell of orange blossoms is about as good as it gets. Jenny and I have orange and lemon trees, whose scent travels from one end of the yard to the other this time of year. 

So what does the smell of an orange tree have to do with “morphology,” whatever that is? Actually, quite a lot. Morphology is the branch of biology dealing with the form and structure of animals, plants, and their parts. Watching the changes in the citrus trees as they flower and ultimately produce fruit is truly fascinating. A biologist, which I am not, could probably teach an entire class just using the photos taken in our yard.   

With the daily changes in the flowers, honeybees, other insects buzzing about (not to mention the smells), and the expectation of the fruits yet to come, the trees are worth a visit on almost any spring day. 

The picture included here shows all we need to have a basic discussion of orange and lemon tree morphology as it relates to reproduction. Of course, there is a bee. Estimated to have a sense of smell about 100 times that of human beings, the honeybees arrive long before I smell or see the trees' changes in the spring. And they are a huge help in moving pollen from where it is to where it needs to go.  

Delicious orange blossom honey is just one side-benefit! Some of the pollen can generally make the short but necessary journey on its own, with just wind to move it, but the bees help ensure the transfer. 

I am partially referencing an online video from the U.S. Botanic Garden by Dr. Susan Pell. You can find it by searching for “Morphology: Flower structure of citrus.” Regarding our photo, let’s refer to the three clusters of flowers as top, left, and bottom. 

Citrus flowers are generally five-petaled, white, and fragrant to attract our insect friends. The left flower shows an early look as the pistil (female part) is developing. It includes the stigma (bright yellow tip, which receives the pollen), its long stalk (style), and the green bulb at the base, the ovary, which will become the fruit.   

The bottom flower now adds a view of the stamens and anthers (male parts), which are pollen-bearing tips on long white stalks surrounding the pistil. The pollen must get from here to the stigma, whether by wind, gravity, or insects. Finally, the top flower shows just a remaining pistil and ovary, which will hopefully be an orange or lemon one day. 

Spring brings lots of wonderful changes – and pollen – to the Lowcountry. As we sneeze, wipe our noses, and rub our eyes for a few weeks each year, it’shelpful to remember the amazing reasons for it all.