Gnats in the Pulpit

Gnats in the pulpit

by Linda Curtis

Gnats in the pulpit

Why aren’t bees the pollinators of Jack-in-the pulpit? Bees are attracted to bright petals and sweet nectar, of which the “Jacks” have neither. Instead,they exude musty mushroom aroma that attracts gnats fly under the arched spathe hood, bonk their heads and fall into the base. Although it’s dark down there, that’s where the flowers are. If the gnat falls into a male plant, it will wander around in the base, getting messy with pollen, until it can get up and out. And where does it fly to? To that wonderful aroma of its larval home in decaying mushrooms, now emitted from the female plant sometimes called Jill-in-the-pulpit.

Jack-in-the-pulpits germinate from seed; young plants may have both male and female flowers in their spadix or pulpit. Eventually, they are either all male with stamens and pollen, or all female with ova that become red fleshy berries after gnats carried pollen to them from a male plant.

Usually, plant economics determines whether a female plant will remain female, or become a male the next year. An abundant year with many berries depletes the bulb-like corms in the soil. As a result, not enough food storage determines that the plant will be male next year and only produce stamens with pollen deep in the base. Pollen is less expensive to make and the males can build up their corms with the food produced in the leaves.

Next year, voila, a female plant can produce a large head of berries if enough gnats bearing pollen again fly up into the hood and fall down to the female stigmas in the base. While the male plant has entries in and out of its basal flowers, the female has only entries, no exits, and the gnats, along with some thrips, become detritus at the base, g’naturally.

This article published in the Wisconsin Entomological Society Newsletter, 2018 by Linda Curtis, author of Woodland Carex and Bog-Fen Carex of the Upper Midwest.

Text from image

Arisaema triphyllum


The pulpit or spadix has either male or female flowers.

Gnats are attracted the fungal like aroma and carry pollen from a male plant to a female plant.

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