The Floral Backup Plan

Jewelweed (Impatiens capensis)

Jewelweed (Impatiens capensis) is blooming this week at my house (and has been for a little while). I had one plant last year, an unexpected plant from a stray seed in one of my pots. This year it is in numerous pots as well as growing up in the leaf litter around the pots; annuals apparently don’t always need a lot of root space. One plant is growing in the ground where a seed was transported further away.

This tall, succulent plant is one of our native annual plants; annual plants create a lot of seeds to ensure that the next generation makes it. Since I have more plants this year, I’ve noticed they are susceptible to deer browse. Such browsing would reduce the plant’s chance of reproducing, but this plant has a backup plan.

In addition to the pretty flowers that we see, jewelweed can form some cleistogamous flowers that self-pollinate and create more seed. The showy flowers that we see are chasmogamous flowers. The cleistogamous flowers require less energy from the plant, especially for one that was damaged by grazing. I read an interesting statement from this article: “If the plant is predetermined to develop into both chasmogamous and cleistogamous flowers, we called it dimorphic cleistogamy. Very often, dimorphic cleistogamous flowers occur at different times or in different locations on the plant.” While I already knew that violets can produce cleistogamous flowers at the base of the plant, the article also mentioned that our native American hog-peanut (Amphicarpaea bracteata) does as well (that might explain why I have so much of that too!).

Above, left to right: a seed and the remains of the seed pod; a new seedling; and one of the showy flowers (and it looks like there's an ant inside it).

Many of us know that jewelweed is also called touch-me-not, a reference to the explosive seedpods that open when you touch them. This allows the plant to eject its seeds further away from the original plant. The seeds from the cleistogamous flowers often drop closer to the plant.

Seeds from showy flowers are cross-pollinated by insects and help to create genetically diverse offspring, a benefit to the species in general. Seeds from the cleistogamous flowers are not genetically diverse and are produced as a backup plan to keep the population going until more favorable conditions exist. I know you’re hoping I’ll show you one of those cleistogamous flowers but I haven’t been able to identify one. I found a statement that “Cleistogamous flowers are very small (about 1 mm long) and are borne near the bases of the leaves,” and I found this article with one photo.