Thursday, June 07, 2012

Srtanger than fiction

A couple of blocks away from us, a neighbour cultivates figs. He has an incredibly neat front lawn and flower garden, with a fig tree planted at each corner. He pampers these trees, pruning carefully in the fall, painting the trunks white to ward off pests, manicuring the ground underneath. And the trees respond in kind, presenting him with a bumper crop of figs year after year.

A few weeks ago, I noticed that his trees were still completely bare, although the rest of his garden was flourishing. Maybe it was just that I hadn't been noticing the date on previous years, but now I started to wonder what had gone wrong.

Then, last week, both trees had suddenly burst out; not in leaves, not in flowers, but in fully-formed fruit. Amazing!

On Saturday, I dropped into my son's house, and he took me on the usual tour of his garden. And there, along the fence, was an infant fig tree, with one fig. I told him about my neighbour's fig trees, which now had leaves, too, and got a lesson in not jumping to conclusions.

Those appetizing pear-shaped green things are flowers, not fruit. Not yet, anyhow.

Low-hanging figs, this afternoon

 What my son told me, and I confirmed later, on multiple pages on the web, (not that I disbelieved him, but this was too improbable, really!) was that fig flowers are inside-out. Each stalk bears many microscopic flowers, all turned inwards to face each other, with the backside, (the outside, to us) encased in their own thickened stem. The entire structure is called a synconium. (1)

But the function of a flower is to attract pollinators so as to produce fertile seeds. How does a flower hidden away in a tightly-sealed package manage it?

When the flowers are ready to be fertilized, they emit an aroma attractive to a tiny female wasp of the family Agaonidae. These wasps, tracking the scent, find the entryway at the bottom of the synconium, and burrow their way through, usually losing their wings and antennae in the process. It's a tight squeeze.  BugGuide has a photo of a fig cut through the middle as the wasps enter (2); it's like trying to crawl into a house through the dryer vent.

Once inside, the wasps set about laying their eggs, inserting their long ovipositors into each flower style. Some are longer than others; the longer flowers end up being pollinated, but the wasp lays no eggs there, so the flowers set seed. Where the wasp lays her eggs, the larvae grow and feed off the tissue of the ovary. (3)

Once the new generation of wasps is fully grown, the males chew their way out of the parasitized flowers, mate with the females, chew their way out of the opening at the bottom of the fig, and die. The females then leave the figs without losing essential body parts, and fly off to find a new fig.

This is all complicated by the circumstance that each species of Ficus has its own variants of this procedure, and is set up to be pollinated by its own specialized species of wasp. (4) Some are even pollinated by a wasp with too short an ovipositor to lay eggs successfully, which means that they die without leaving progeny; the replacement generation has to come from an entirely different species of fig.

My neighbour's trees are doing fine.

After the wasps leave, the synconia ripen, changing colour and scent, to attract birds and other fruit eaters, including us. If the flowers have set seed, the resulting fruit has a nutty flavour; seedless figs are more bland.

Figs are tropical plants, but some varieties do quite well here in the mild Lower Mainland. I looked up Ficus in my tree book, and was again surprised; the genus includes such oddballs as the banyan tree, the strangler fig, the creeping fig, and the sandpaper fig. (5) Some are trees, others are vines or shrubs.

This one, climbing the wall of the Paneficio in Strathcona, is a sturdy vine.

I have, or had, a photo of a vine fig in Vancouver that grew over the roof of a house and up the wall of the apartment building next door. When I saw it, it was dangling over the roof several stories up.

  1. US Forest Service
  2. BugGuide photo
  3. Figweb: How fig trees are pollinated.
  4. Figweb: Who pollinates fig trees?
  5. Wikipedia: Ficus


  1. Amazing. Thanks!

  2. It turns out that the Fig was the first cultivated food plant.

    "Early Domesticated Fig in the Jordan Valley" Science 2 June 2006:
    Vol. 312 no. 5778 pp. 1372-1374
    DOI: 10.1126/science.1125910

  3. So interesting. Who'd a thunk?!

  4. My mother had two fig trees and I loved to go out and pick the luscious fruit. But I never knew about the pollination process. Very interesting. - Margy

  5. Gary, Thanks! From the abstract: "which preceded cereal domestication by about a thousand years." Interesting!

    Eileen, "Who'd a thunk?!" Now, that would have made a better title!


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