TREES, PLEASE! Ficus, Figs and Fascinating Tree Sex

By Robin Y Rivet.


Photo credit: Barbara van Amelsfort, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons.)

Ficus carica - edible fig: cross section showing syconium.


Did you ever wonder why you don’t see flowers on fig trees? If you eat figs, you basically munched on them.


“Invasive roots” is a term that typically tarnishes the reputation of the Ficus genus of ornamental figs, even before we consider how wildly they procreate. Although maligned for root damage when inappropriately planted in small spaces, their aggressiveness also makes them resilient to tough conditions, quite desirable in our increasingly warmer urban regions. But to make reproductive seeds, these evergreen trees must rely on fig wasps.


The life cycle of the fig wasp (family Agaonidae). Photo credit: "By courtesy of Encyclopædia Britannica, Inc., copyright 2019; used with permission.")

Edible fig trees – Ficus carica cultivars are also vigorous and drought tolerant, and produce diverse and delicious fruit. Humans have been domesticating figs for over 11,000 years, and California grows many cultivars found around the world, including Smyrna, San Pedro and Common fig types. Because edible fig trees are deciduous, they are also much less likely to have invasive roots. In fact, Cal-Poly SLO suggests that the edible fig’s root hazards are low. Surprised?


Keep in mind, figs are not really “fruits” at all. By definition, a “fruit” is a fleshy or dry ripened ovary of a flowering plant, enclosing the seed - or seeds. Except for what’s called the “common fig” - which is basically seedless, most “fig fruit” development requires fig wasps for pollination. That “mutualism” results in exotic reproductive habits.


Botanically speaking, all figs are syconiums, not fruit - which means they resemble an inside-out flower that prevents airborne pollination. There’s a small opening at the blossom end called an “ostiole” that allows only species-specific pollinating wasps to enter. Amazingly, although there are over 750 varieties of figs, each with its own specific wasp. As mature female wasps try to squeeze through the ostiole carrying pollen, their wings and antennae rip off. Yikes! Once inside, they lay their eggs into ovules and randomly pollinate tiny female flowers that potentially become reproductive seeds. Their eggs become encased in protective galls that nurture the young wasp larva. However, at this point - the now wingless, female adult wasp perishes inside the “fig”. Hmmm.


Larvae that hatch first are now blind and wingless males, who promptly seek out females for mating. But since the females haven’t hatched yet, males go ahead and mate through the gall with the helpless, immature female larva still tucked inside. Imagine that? Since males cannot fly, after mating they attempt to tunnel out to freedom through holes in the fig “skin”. While some escape, others remain stuck inside to die. Eventually, the newly-hatched female larva are “born pregnant”. These fertilized female wasps now collect some of the pollen from the mature internal male flowers - that were earlier pollinated by their mother. Then the females exit through the tunnels - beginning the process over again. For anyone confused by all this, I am sharing an amusing fig sex video from PBS, (note to Karen imbed PBS video if possible) which clarifies this process with visuals and humor.


Photo credit: <https://creativecommons.org/licenses/by/2.0>, via Wikimedia Commons.)

Ficus auriculata - Roxburgh Fig, San Diego Botanical Garden, Encinitas, CA Cultivar413 from Fallbrook, California. The fruit are inedible unless pollinated by a native Asian wasp.


Now, if this entire scenario causes you to question whether you ever want to eat another fig - relax. Almost all commercially grown dried figs in the United States and most fresh ones are self-fruitful. However, if you home grow hybrid San Pedro type figs like ‘Desert King’, or the California Smryna-type ‘Calimyrna’, their main crop must be “wasp-pollinated”. Yum.

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To Learn More:

· UC Backyard Orchard Tips: http://homeorchard.ucanr.edu/Fruits_&_Nuts/Fig/

· Read about many edible fig varieties here: http://figs4fun.com

· An MG general resource pamphlet: https://ucanr.edu/sites/mgslo/files/308954.pdf


Member Robin Rivet is an ISA Certified Arborist – contact her: treetutor@gmail.com