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Pollinating inside-out fig requires wasps

Seeds are actually the flower growing on the fruit’s insides

By LEE REICH, Associated Press
Published: February 9, 2017, 6:00am

My barely heated greenhouse kept me in fresh figs well into fall, but decreased light and increased cold have made those juicy, ambrosial fruits a mere memory.

Now I go to the store and purchase dried figs, to me a totally different fruit: super-sweet, a bit crunchy and, of course, not at all juicy.

It’s winter, and plants no longer clamor for attention, so let’s focus on that crunchiness of dried figs. It comes from seeds, which I would never find in my own figs’ fruits. Botanically speaking, those “seeds” are the real fig fruits. What we commonly call a fig “fruit” is actually a hollow stalk whose inner wall is lined with the true fruits. (With that disclaimer off my chest, I’m going back to calling the hollow stem a “fruit” and the crunchy things inside the “seeds.”)

Those seeds result from pollination, which is no small feat for what might be thought of as an inside-out fruit.

For most kinds of fruits to develop, pollen from a male flower, or the male part of a bisexual flower, must first be dusted onto the female part of the flower. But Smyrna — the most commonly sold variety of dried fig — has no pollen.

Fig pollination is brought about by pressing into service a tiny wasp. Smyrna fig trees were introduced into California in the 1880s, but until fig pollination was understood, all the figlets on the fig trees merely dropped to the ground.

Little helpers

Mediterranean farmers long ago discovered that Smyrna fig trees could be made fruitful by hanging among their branches fruits of inedible, so-called wild goat figs, or caprifigs. The caprifigs supply the needed pollen, which is carried into the developing Smyrna fruits by that tiny wasp.

The wasp is called Blastophagus, and her work is called caprification. Blastophagus’ eggs, as many as 600 in a single fruit, develop inside the caprifigs. At certain times of year, which correspond with caprifig fruit development, male wasps awaken, fertilize still-sleeping female pupae, and then die without ever leaving the caprifigs.

Female wasps emerge soon after, just when the male caprifig flowers are shedding pollen. As the wasps wend their way out of the caprifigs, they inadvertently pick up pollen.

Once outside a caprifig, Ms. Blastophagus begins searching for an unpopulated caprifig in which to deposit her eggs. Fig pollination occurs as she frantically moves from flower to flower trying to lay eggs.

Eventually, the poor wasp dies from exhaustion.

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