Jewelweed Goes Ballistic at The Woods

Walk down the Valley Trail and become surrounded in this moisture-loving plant. Early in the spring you can start to see the youthful sprout pop up out of the ground everywhere. Now that we're into autumn, the fruit of this plant is looking about ready to pop! Some of the plants have even grown so high they could tower over you (depending on your height, of course)! The tantalizingly plump fruits beckon you to give them a gentle squeeze and – POP! – seeds burst in all directions and suddenly that fat little pod has disappeared before your eyes.

How does it do that?!

If you're quick enough (or if the pod is slow enough), you might be able to catch the pod right after it opens. You might notice a bunch of curled up plant parts and maybe a few seeds left behind. You're looking at the aftermath of a ballistic seed dispersal mechanism.

When a jewelweed fruit is ripe, there is so much pressure built up inside that the slightest touch will cause it to burst. Not too many other plant fruits will do this. When a banana is ripe, for example, it does not go ballistic when you grab it for your lunch. Inside the pod is a columella, surrounded by the seeds, and the whole fruit is enclosed by a few pieces called valves. The seeds are not attached in any way so when the pod is squeezed, the valves scrunch up, the columella collapses and the seeds get pushed out.

Deconstructed seed pod. From left: curled valves, columella, seed.

Read more

An article was published in the Journal of Experimental Botany where scientists quantified the ballistic dispersal mechanism of these seed pods. Read this fun and fascinating article here.

See for yourself

We have a lot of spotted jewelweed (Impatiens capensis) all around the woods. You'll find it especially near water like along the Valley Trail and the beaver pond. Stop by while the seeds are still ripe and watch the seeds launch!


Blog post by Anna Leiss