Plant of the Week: Jack in the Pulpit (Arisaema triphyllum)

This is one of the most unusual of all the native woodland wildflowers. When you say you are looking at the flower, you are not really looking at the flower but rather the inflorescence or cluster of flowers because the individual flowers are tiny and hidden in the "jack" which is located inside the rolled leaf-like structure, the "pulpit." This is a unique species in that individual plants are either male or female.  Most plants have both flowers on the same plant.  In this species to see the individual flowers, which are located at the base of the spadix (the pulpit) inside the jack or jill as it may be which is called the spathe.  If it is a jack you will see tiny yellow to brown thread like anthers and if it is a female you will see tiny green berries. All members of this mostly tropical plant family has a similar structure and while rare in nature, people are familiar with this family because of the calla lilies, peace lilies, philodendron, and caladiums.  Most people are unaware that this plant can change sex multiple times over it's 20 year lifespan.  Plants that have grown for a sufficient number of years that get large enough and have enough resources are often females.  However, when times get tough, they can revert to becoming a male or non-flowering plant.  So what determines the sex of this plant?  We have all heard the rumors about size and does size matter?  In this species the answer is definitely yes, size matters! Bigger plants are usually female plants. The sex of the current year’s plant is determined by the size of the previous year’s root storage structure, called a corm. Larger corms yield females, while smaller corms yield males or nonflowering plants. In addition, in those plants that have produced larger clusters of the red berries, the next year they are most likely going to be male plants. Another factor affecting sex is that skunks, slugs, and deer will devour these plants, even though they contain oxalate crystals that makes them distasteful.  Since this species has both male and female flowers, how do they get pollinated because the flowers are not accessible to bees?  Basically, the jack produces a fungus type odor that attracts its primary pollinator, the fungus gnat.  Unfortunately, once the female fungus gnats get down to the base of the flowers, the tube is too slippery and they can not get out, hence dying at the bottom of the tube along with their valuable pollen.  If the flowers were pollinated the red berries will begin to grow and by the end of the summer the female plants can have large, showy clusters of red berries. Immature plants usually one have one leaf with three leaflets and mature plants typically have two leaves with three leaflets each. These are easy to grow in the woodland garden as they tolerate a wide range of soil pH and it appears about the only thing that will kill the corms is excessive water in the winter and spring.