Jack-in-the-Pulpit: What’s Under the Hood?

This week’s blog post was written by Stewardship Technician Max Dunn

Over the past few weeks, the stewardship crew has been hard at work pulling garlic mustard. As we grid the parks for these pesky weeds my eyes are also searching for Jack-in-the-Pulpit. Since we are walking every square inch of the parks to eradicate garlic mustard, I figured I should take some time to appreciate another plant. Life is all about balance right?

Jack-in-the-Pulpit flowering structures are composed of a modified leaf called a spathe and a pillar-like spadix which houses many small flowers and eventually striking red berries.

Jack-in-the-Pulpit (Arisaema triphyllum) is a widespread, eccentric perennial of woodlands that varies greatly in pigmentation, alters its sex overtime, and holds insects captive. This plant is easily recognized by its flowering structure, which is equipped with a hooded spathe and a pillar-like spadix. The spathe is a modified leaf that wraps around the spadix. This leaf initially caught my attention while gridding for garlic mustard because of their unique color patterns, ranging from a pure pastel green to a combination of dark green and waxy maroon. I am most interested in the underside of the spathe hoods since they create beautiful patterns, especially when the waxy maroon pigmentation contrasts pastel green veins.

The spadix also varies in pigmentation, but I found they tend to be green in Oakland Township. This pillar-like structure contains small, closely-arranged flowers that are either male or female depending on the plant. Nutrient reserves in the plant’s below ground corm (a modified stem for energy storage) helps determine the sex of the flowers. Plants with small corms and fewer stored nutrients are male, while plants with larger corms and more nutrient reserves are female. Larger corms allow plants to produce a second set of leaves and invest energy in female flowers that will produce striking, inedible red berries that are on display in the fall.

An interesting way to identify the sex of these plants is by looking at an insect trapping mechanism on the lower part of the spathe. Male spathes are equipped with a small little crook that allows pollen-covered insects like thrips and flies to easily exit and fly to a female flower. However, insects do not have an easy escape route in female plants since they lack this small crook in their spathe. With no easy escape these insects naturally spend more time near the flowers of the female spadix, frantically walking around and pollinating the flowers of the spadix more effectively.

These forest floor plants are an awesome sight if you take a second to look under the hood. The color variation of the spathes are beautiful and fascinating. If you catch a female at the right time you might just find a victim of successful pollination! Jack-in-the-Pulpit will be flowering for a couple more weeks so enjoy these unique plants before they finish flowering for the year. Comment below if you have a favorite Jack-in-the-Pulpit color variation!