THE FIG AND THE FIG WASP
The Power of Coevolution and an Ancient Tale of Fatal Attraction
Every Southern California home orchard should have a fig tree. They are perfectly suited for our Mediterranean climate, they feature lusciously tropical foliage, and they offer one of the most flavorful fruits nature has to offer.
But sometimes we fall in love with a plant not only for its beauty and benefits, but for the story it tells. Figs are an ancient fruit, and the edible fig species (Ficus carica) we know and love is just one member of a vast Ficus genus, a group that has an endlessly complex and fascinating relationship with the environment.
I first learned about the fig wasp while hiking through the rainforests of Australia. My terrestrial ecology professor’s eyes lit up when he first stopped on the trail and began gesturing to the tropical strangler fig trees overhead, describing how each fig species in the forest has its own special species of fig wasp that is solely responsible for pollinating that tree species. The wasps, in turn, carry out their life cycle within the figs, mating, laying their eggs, and dying. Without the wasps, the trees would cease to exist, and without the trees, the wasps would perish. Amazingly, a similar relationship exists between our edible fig tree, F. carica, and their corresponding fig wasp, Blastophaga psenes.
This tale begins with understanding the background of what a fig really is. A fig is not actually a fruit at all, but a flower, or rather a group of flowers called an inflorescence. Think of a young fig like an inverted bouquet - a cluster of flowers all nestled within the skin of the fig. Figs need pollination in order to reproduce, but there is an obvious challenge in hiding your flowers all within the flesh of the fig. There’s no way traditional pollinators like bees and butterflies can get to those flowers - but that’s where the specialized fig wasp comes in.
All fig wasps are born within a male fig, known as a caprifig, which are small and unpalatable (these are not the figs we are eating). Males are born in, breed in, and die in the same caprifig, never leaving the confines to witness the outside world. Therefore all the work is left to the female fig wasp, who must venture outside to find another caprifig to lay her eggs in. Upon locating another caprifig, the female burrows inside, lays her eggs, and dies, completing the life cycle. The act of entering the fig tears off her wings, so she only has one chance to get it right.
Sometimes the female fig wasp encounters a female fig (the edible, delicious figs we know) instead of a caprifig, and climbs inside. On her body she still carries the pollen from the caprifig she was born in, and in the commotion she spreads the pollen around within the female fig, pollinating the flowers. Unfortunately, she cannot lay her eggs within a female fig, and the female fig wasp is destined to die trapped inside.
Ficus carica is a unique species in that many of our most common cultivars, such as ‘Brown Turkey’, are parthenocarpic, which means they actually don’t need to be pollinated at all in order for the fig to fully develop to maturity. Therefore, many of the figs we buy at the grocery store never actually encountered a fig wasp. But other popular cultivars, such as the delicious ‘Calimyrna’, are non-parthenocarpic, and completely rely on the fig wasp in order to produce figs. If the figs go unpollinated, they will simply drop from the tree before fully developing.
Even parthenocarpic figs can benefit from pollination, even though they don’t need it. Research has shown that pollination by fig wasps can yield figs that are firmer, larger, more flavorful and store longer. The photo below shows the development of a pollinated (top) and unpollinated (bottom) fig over time from a parthenocarpic cultivar. This photo speaks for itself, as the pollinated fig is strikingly larger, brighter, and more enticing.
Credit: Rosianski, Yogev, et al. "Advanced analysis of developmental and ripening characteristics of pollinated common-type fig (Ficus carica L.)." Scientia Horticulturae 198 (2016): 98-106.
Needless to say, learning this tale of coevolutionary fatal attraction quickly convinced me that I needed a fig tree of my own. It is growing in my parents’ backyard, thriving in the hot California sun and our compact granite soil, sporting clusters of amethyst fruitlets along the branches for many months out of the year. Our fig tree is a parthenocarpic cultivar, but based on its large, vibrant fruitlets, I would like to think that some fig wasps have made their way to the tree, as they have for thousands of years.
If this tale of figgy wonder has inspired you as it inspired me, visit Roger’s Gardens to peruse our latest selection of fig varieties. We have everything from the tried and true to new super dwarf varieties, perfect for any home garden. And as you enjoy your first home-grown fig, remember that you are indulging in a beautiful phenomenon of natural history.