It’s often said that the Jack-in-the-pulpit changes its sex as it ages. Is that really true?
This is an excerpt from the Wild Ones Journal
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Jack-in-the-pulpit (Arisaema triphyllum), was among the first plants that I started from seed, under the tutelage of Roberta Case. Some members of the Michigan Chapters of Wild Ones may remember Roberta Case “Boots”, who passed away a number of years ago.) It was then that I first read a description of the growth habits of this plant. The story goes that it starts life as a male, and in later years, when it has grown two leaves, it becomes a female. This scenario bothered me; it felt like large pieces of information were missing or somehow misrepresented.
I quote the following description of Jack-in-the-pulpit life in process from the notes of botanist W. H. Camp, written around 1930, while he was a doctoral student at Ohio State University, now archived by New York Botanical Gardens where he spent a good deal of his professional life.
Studies by the writer since 1925, both on marked plants in the field and in experimental plots, have shown that Arisaema triphyllum begins as a weak, non-flowering plant with a small corm. This is true for both the seedling plant and the plant having its origin in a vegetative off-shoot. After several years of growth – generally more than three, depending on the habitat – the plant has its first flowers. The first inflorescence is generally small and contains only staminate or male flowers.
Since the habitat is a decided factor in the development of the individual, subsequent stages in the life history are closely linked with the environment. If the plant is in a moist, rich woods and little disturbed by animals, it increases in size from year to year, both in the aerial and subterranean parts. In several years a few carpellate or female flowers may appear on the spadix, sometimes mixed with the staminate flowers, but generally near the base of the inflorescence. This intermediate or monoecious stage (with flowers of both sexes represented on the same plant), generally lasts several years, the proportion of carpellate flowers becoming greater until the whole inflorescence is made up of carpellate flowers.
Camp describes the process just a little more specifically than the old wivestale does. I asked Dr. Anton Reznicek, the curator of the University of Michigan herbarium, for his thoughts:
I’ve not been fond of loose usage of male and female (as in Arisaema). This is a plant that is a monoecious hermaphrodite. Most plant species are hermaphrodites, with perfect (bisexual) flowers, but it is also common to have plants that have male and female flowers scattered on the same plant – think ragweed. What is unusual about Arisaemais that the plant has the ability to control how many male and female parts it produces. So I think the interesting element here is the sexual expression – male one year, female another, monoecious yet another year, and, of course, also vegetative – and how this is controlled.
The plant is always the same – it does not change sex as such, it changes how its innate (and unchanging) bisexuality is expressed, and this includes being vegetative. We never say that a vegetative individual of a plant has changed its sex to simply “none” because it does not flower that year! This is the same situation.
Careful use of terms should clear up any confusion, and I prefer the use of carpellate and staminate as opposed to male and female, with all the implications those terms carry for us animals.
Dr. Reznicek’s comments bring the large pieces of the puzzle together. And a puzzle it truly is.
By Maryann Whitman