I originally published this piece last Spring, and instead of writing a whole new post on my favorite late-spring ephemeral, I present it to you again! This essay was so much fun to investigate and write. I hope you enjoy it, and more importantly, that it inspires you to go peer into a nearby Arisaema triphyllum.
note: I’ve included a small glossary of plant terminology at the end, and have also inserted some definitions along the way so you don’t have to interrupt your reading to scroll down. The words defined in the glossary are bolded where they first appear in the text.
Jack-in-the-pulpit is a peculiar plant.
The hollow, hooded form is striking— it’s hard to resist making a closer inspection. As you examine the mysterious flower, you’ll undoubtedly find yourself lifting the striped mantle to reveal the smooth, elegant spadix within.
The coloration of the spadix and striped spathe varies from a dark near-black to a pale, fleshy green. Sometimes when you peer beneath the spathe’s veil, the spadix trembles, bringing to mind a cloaked figure or a snake poised to strike. Three upright leaflets fan out behind the inflorescence, adding to the drama.
Spathe: a single bract that surrounds the spadix— on jack-in-the-pulpit, this is the entire striped outer “pulpit” that encircles the “jack”
Spadix: a flowering spike, on jack-in-the-pulpit it’s the “jack,” which has many small flowers hidden at its base
Bract: a modified leaf
Inflorescence: the entire flowering structure of a plant— on jack-in-the-pulpit, the actual flowers are hidden inside the spathe at the base of the spadix. The entire structure pictured below (minus the leaf) is the inflorescence.
lifting the spathe’s hood to reveal the spadix
Jack’s bizarre shape is often compared to that of a pitcher plant. And although it is not carnivorous, it does trap the fungus gnats that pollinate it, which die inside the spathe after futile attempts to escape. Let’s back up for a second though.
Jack-in-the-pulpit is dioecious, a word stemming from the ancient Greek dioikía, which translates to “of two houses.” It means that the male flowers and female flowers are on separate plants, preventing self-pollination. This is uncommon in and of itself: only ~6% of flowering plants are dioecious. But Jack-in-the-pulpit takes its rare sexual expression one step further, possessing the ability to change sex from year to year.
Jacks start out as single leaves, absorbing nutrients and sunlight that will eventually help them bloom. When they first muster the energy to put out an inflorescence it’s male, with flowers that consist of stamens and pollen– this takes less energy than producing female flowers. After a couple more years, when the plant has stored up enough energy in its corm, it produces the female flowers that when pollinated create fruits and seeds. If the plant’s energy is depleted, for example if there’s poor conditions or if it used up its stores producing fruits, it can revert back to male the following year, and so on.
Self-pollination: pollination in which a flower is pollinated by its own pollen or that of a flower on the same plant
Stamens: the male fertilizing organ of a flower, usually possesses pollen
Corm: a modified underground plant stem that serves as a storage organ
The females are often larger and sometimes have two leaves vs. the typical single compound leaf of males. The two sexes differ in another key characteristic– the males have a small hole in the base of the spathe that allows pollinators to exit the plant, while the females have no hole, trapping the pollinators that visit them.
The primary pollinators of Jack-in-the-pulpit are fungus gnats. They’re attracted to a scent the plant emits that mimics fungus. Don’t bother trying to get a whiff though— this scent is imperceptible to humans.
Compound Leaf: a leaf comprised of two or more distinct leaflets joined by a single stem (in the case of Jack-in-the-pulpit, each leaf has three leaflets)
note the three leaflets which make up each compound leaf
How it works: a gnat finds its way into the hollow spathe of a male plant and searches for fungus, bumping into the pollen-laden stamens along the way. The gnat, finding no fungus, decides to exit the plant. But if it tries to fly up and out the way it came in, it strikes the hood and falls back down to the bottom of the tube. It becomes disoriented; the hood also blocks the light which makes it hard for the gnat to navigate. The slippery walls prevent the gnat from crawling out. It might repeat its exit attempts any number of times, collecting more and more pollen, before eventually finding its way out of the small hole at the base of the spathe.
Ideally, the gnat continues its search and is soon duped again– this time by a female plant. The gnat enters the plant the same way, bumping into the female flowers and depositing the pollen it collected earlier, pollinating the plant. But with no exit this time, the gnat eventually dies inside the spathe. The prevailing theory is that the female plants evolved this adaptation to force the gnats to stay inside them for as long as possible– increasing the chances of successful pollination.
While reminding myself of the details of this fascinating pollination process, I stumbled on a small mystery. All of the sources I found online maintain that Jack-in-the-pulpit is dioecious, as I described above. However, as I searched, I came across a few sources that mentioned that an individual plant can sometimes produce a combination of male and female flowers on a single spadix. The proportion of male to female flowers in that case determines the functional sex of the plant. These sourcesstate that despite Jack-in-the-pulpit’s ability to occasionally produce both sexes of flower on one spadix, it still cannot self pollinate because either the male or the female flowers on such a plant are inert. A couple sources went into greater detail, saying that when there are two sexes of flower on one individual, they mature at different times, making self-pollination impossible.
This raised so many questions: how commonly do Jacks actually produce both male and female flowers? When an individual does possess both male and female flowers, will it have the escape hatch typically found in unisexual males? What about the way these plants are categorized– if they have the ability to produce both male and female flowers on the same individual, are they truly dioecious? And does the staggered male vs female bloom timing ever effect cross-pollination?
I’m sure a botanist could answer these questions, but I don’t personally know any botanists. And besides, when presented with a puzzle I would almost always rather investigate myself— to the extent that that’s possible, anyway.
Unisexual: when a plant only has the reproductive organs of one sex— dioecious plants are unisexual
Cross-pollination: pollination in which a flower is pollinated with pollen from a separate plant
a solitary female Jack, quite large, with two compound leaves
Luckily, the opportunity to answer some of these questions arose spontaneously. I was out doing a natural community visit a few days ago (this time to a Mesic Clayplain Forest and a Sand-Over-Clay Forest– summary forthcoming), when I happened upon dozens of Jack-in-the-pulpits. This natural community provided the perfect conditions for them: moist, nutrient rich soil, with the right combination of shade and sunlight. I decided to do a quick survey and see how many were male, how many female, and whether I could find any possessing both male and female flowers.
I started looking around and quickly realized that there were far more male than female plants. I gently unfurled a few of the spathes and peered inside— the actual flowers are clustered at the base of the spadix. It’s really easy to tell the male flowers from the female flowers once you’ve seen them: the female flowers each have a bright green ovary and a fuzzy white stigma, while the males are pale cream to purple with teensy u-shaped stamens and pollen.
Stigma: the part of the flower that receives the pollen
left: female flowers, right: male flowers
I was able to see the male escape holes in-person for the first time too, and compare those to the corresponding area on the females. I’d always wondered what these “holes” looked like, and they weren’t what I was expecting. They were more like indentations than actual holes.
left: “escape hatch” on a male plant, right: the corresponding area lacking a hole on a female plant
After carefully examining several Jacks, I found what I was looking for: a plant that possessed both male and female flowers. Looking closely, it appeared that the male flowers were not producing pollen.
two individuals possessing BOTH male and female flowers
I walked around more and noticed a few patterns. Some of my observations confirmed what I already knew: the female flowers were larger and tended to have two compound leaves, while the males were smaller and greater in number. My exit hole question was answered— the few individuals I found that possessed both male and female flowers all lacked an escape hatch. Surprisingly though, as I examined more of them, I noticed that some of the male flowers on these individuals seemed to possess both pollen and fully formed female flowers. I say seemed because that’s how it appeared to me, but I can’t be sure, I am not an expert. Though even if the male flowers died before the female flowers matured, isn’t it likely there would still be plenty of pollen sitting in the bottom of the spathe, ready to be transferred to the female flowers by an unwitting gnat?
I have more questions now than I did before I investigated. I’ve come to expect that both from nature and from self-study, though: the more you learn, the more you understand how much you don’t know. I am at the very least glad to have finally peered into the guts of these clever plants and seen the place where so many brave gnats have met their untimely ends. And when clusters of bright red berries appear amidst the lush forest floor in late summer, I’ll think about the sacrifice they required, the tiny green flowers they once were, and the years of stored energy it took to create them.
the bright red fruits of jack-in-the-pulpit
All illustrations and photos are my own.
Note: This is the fourteenth in a series of posts on spring ephemeral wildflowers.
Previous posts:
- Skunk Cabbage
- Hepatica
- Bloodroot
- Blue Cohosh
- Dutchman’s Breeches
- Yellow Trout Lily
- Carolina Spring Beauty
- Red Trillium
- White Trillium
- Early Meadow Rue
- Large-flower Bellwort
- Wild Ginger
- Two-leaf Miterwort
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GLOSSARY
Spathe: a single bract that surrounds the spadix
Spadix: a flowering spike
Bract: a modified leaf, sometimes showier than petals
Inflorescence: the entire flowering structure of a plant
Dioecious: having male and female flowers on separate plants
Monoecious: having male and female flowers on the same plant
Self-pollination: pollination in which a flower is pollinated by its own pollen or that of a flower on the same plant
Cross-pollination: pollination in which a flower is pollinated with pollen from a separate plant
Stamens: the male fertilizing organ of a flower, usually possesses pollen
Stigma: the part of the flower that receives the pollen
Pistil: the female reproductive part of a flower
Corm: a modified underground plant stem that serves as a storage organ
Compound Leaf: a leaf comprised of two or more distinct leaflets joined by a single stem (in the case of jack-in-the-pulpit, each leaf has three leaflets)
Unisexual: when a plant only has the reproductive organs of one sex— dioecious plants are unisexual
This post was originally published here.
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