Guest post by Pati Vitt
The weather has varied a lot so far this spring. Minor snow squalls and hailstorms trade off with wonderfully warm, sunny days, which seem to call out, encouraging us to find the signs of spring. When the season brings all the beauty and promise of plants and flowers emerging from the winter, I feel as if I am seeing friends old and new once again. It’s rather comforting to know that regardless of what occurs in human society, spring carries on in the Lake County Forest Preserves in northern Illinois.
Many of the floral signs of spring are ephemeral, created by healthy populations of plant species that only emerge above ground for six to eight weeks—between the start of the spring warm-up and the closure of the canopy, when the trees grow a full set of leaves. Their live-fast lifestyle is an evolved response to their shade intolerance. Ephemerals need to finish flowering and fruiting while they have enough sunlight, and also put something away for a rainy day. They stash the sugar they make during photosynthesis in underground storage organs such as corms, bulbs, and rhizomes. The starchy carbon will see them through the winter into the next spring.
Some residents of our woodlands and prairies announce the arrival of spring in understated ways that require careful attention. The early-flowering harbinger of spring (Erigenia bulbosa), and later bloodroot (Sanguinaria canadensis), are two examples. Other signs of spring are exuberant and showy, such as the carpets of marsh marigold (Caltha palustris) at Ryerson Conservation Area in Riverwoods. And of course, no spring display is quite so welcome as large-flowered trillium (Trillium grandiflorum) in full bloom. (This sight is only possible when the white-tailed deer (Odocoileus virginianus) population is stable; otherwise these beautiful plants are eaten out of existence.)
Not all spring wildflowers are showy, though, and not all of them are ephemeral. Arriving later in the season, Jack-in-the-pulpit (Arisaema triphyllum) is one of the most common spring wildflowers in our woodlands. It’s usually entirely green in Lake County. Rarely, some maroon stripes may also be seen on the inflorescence, the reproductive portion of the plant.
Each plant produces a spike of tiny flowers called a spadix that is hidden by a whorled, leafy skirt enclosing the flowering spike so completely it even folds over the top. This bract is called the spathe, and it hides a secret about Jack-, or maybe Jill-, in-the-pulpit. The spadix may have flowers that are entirely made up of pollen-bearing anthers—male flowers. Or the spadix may have only tiny female flowers with no anthers in sight.
Plants that produce a male spadix are much smaller and bear only a single, three-parted leaf. Plants that produce a female spadix are larger and almost always have two, three-parted leaves. One female leaf is often larger than the single leaf produced by even the biggest male plant.
Jack-in-the-pulpit is sometimes used as a model system to explore reproductive costs in plants. Generally speaking, the energy cost for a plant to produce female flowers and then give them the supplies they need to develop embryos, seeds, and fruits is higher than the cost to produce male flowers and pollen, even when pollen is released in copious amounts. With Jack-in-the-pulpit, the cost of supplying embryos and developing fruit is so high that the rate of photosynthesis is also higher in female plants, measured on a per unit leaf area. Simply put, they need more energy.
Along with variable rates of photosynthesis, Jack-in-the-pulpit has another unusual adaptation that helps offset the cost of reproduction. An individual plant can display as male or female in any given year and will “choose” which, depending upon the nutrients available in its corm. Plants that are primarily female tend to cluster in gaps in the tree canopy, while male plants are more prevalent where the canopy is closed and less sunlight is available. When a tree falls, creating a gap, the gender ratio shifts accordingly.
Watching Jack-in-the-pulpit emerge in the later part of the season reminds me spring itself is ephemeral. The gender-changing dynamics of this species fascinated me so much, I selected it as the focus of my dissertation for my PhD at the University of Connecticut. Seeing this plant here in Illinois brings a sense of nostalgia for the woods and fields of New England, and for the first days of life after the birth of my daughter, when life itself was literally brand-new. It helps me feel grounded in my adopted home.
This year, as I watch the trees leaf out from behind windows rather than in-person, I know Jack-in-the-pulpit is out there, following the season. And I know this plant is green, wonderful green, from flowering until it matures its bright, red fruits in late summer and fall. My friend will still be there to greet me when I’m finally able to emerge, too.
Want to learn even more about spring wildflowers? Take a plant-tastic virtual wildflower walk through Ryerson Conservation Area in Riverwoods. Eileen Davis and Mark Hurley, Environmental Educators, share interesting tidbits about species found there, from Dutchman’s breeches (Dicentra cucullaria) to cutleaf toothwort (Dentaria laciniata).