Monday, April 28, 2014

Jack-in-the-Pulpit or Jill-in-the-Pulpit?

After the early spring ephemerals have bloomed Jack in the Pulpit emerges, typically in moist situations. In the SBG they can be found alongside the trail
Jack peeking out over the pulpit edge
that leads from the formal garden to the
bridge over the creek that runs beside the Orange trail . This unusual plant is in the Arum family (Araceae; pronounced: ah-Ray-see-e).  All the Arums have the same reproductive structure: a central column, called a spadix, that bears flowers and is partially or completely surrounded by a spathe. In Jack in the Pulpit the spathe forms the "pulpit" and the "preacher" inside is the "Jack." But it's a little sexist to call every such plant Jack-in-the-Pulpit because the sexes occur in separate plants. A spadix usually bears either all male flowers or all female flowers. So some of the "jacks" are really "jills."

Telling males from females

How do you tell them apart? There are two ways. The jills are larger plants with two leaves, while the jacks have only a single leaf. (What looks like three leaves is really a single leaf with three leaflets.) So if all the pulpits are growing from single leaved plants they are truly jacks, i.e., male.
The second way to sex a Jack-in-the-Pulpit is to carefully open the spathe. By gently pulling apart the overlapping edges of the spathe you can see the flowers on the lower part of the spadix. These flowers have no petals or sepals. If they are plump and green with white centers you are looking at a jill. The jack spadix has numerous small, non-plump flowers with dark anthers and pink pollen.

Deciding to be jack or jill.

Jack in the Pulpit is a perennial plant, so you might think that a single plant would remain the same sex from year to year. But nature is full of surprises. Jack in the Pulpit can change sex from one year to the next. Whether it develops as a male or female apparently depends on how much food it has stored during the previous years growth. If there is sufficient food stored in the corm then a female will emerge the following spring. If not, then the plant will develop as a male, or may not even produce an inflorescence if its stored energy is too little. Now you can understand the reason for the two leaves in female plants. After pollen has been delivered to the ovules the plant must have enough energy to develop its seeds, a process that takes all summer. Having two leaves increases the amount of sunlight captured to feed the growing seeds. Typically, if a plant has assumed the female role in one year, then the energy consumed in producing seeds will be so large that the plant reverts to being male in the next year.

You can find more details about the interesting life history of Jack-in-the-Pulpit in the book by Carol Gracie: Spring Wildflowers of the Northeast: A Natural History, 2012, Princeton University Press.

1 comment:

  1. How interesting and informative! I've been looking at and photographing these plants for a decade, and I didn't know the sex part... Thank you for enlightening me on this subject. I still learn something new every day.

    Jim Fowler, Greenville, South Carolina


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