Bladdernut Seeds: Ready to Float Downstream

Not often, but sonetimes, winter is the best time of the year to find a particular tree species. This week I found a clump of Bladdernut trees (or shrubs) in Eliza Howell Park. The seed capsules still clinging to the stems, noticeable now that the leaves have fallen, were what caught my attention from a distance — and drew me close for a better look.

This clump, made up of trees about 12 to 15 feet tall, is very close to the Rouge River. The trees can easily be passed by without being noticed (I have done it many tines) as they are similar to other small trees that make up the understory of the forest.

The seed capsules are distinctive, one to two inches long, lightweight, and feeling like dried paper. They have been described as “bladder shaped,” the source of the name given to the tree. Each segment of the capsules contains one or more small seeds that, at this time of the year, are dried and loose. The capsule is a rattle when shaken. The seeds are almost the same color as the capsule that holds them.

Bladdernut is native to eastern North America, often found along rivers and streams. (The range map is from the USDA.)

As I examined the seed capsules on the trees, pulling the branches down for a better look, a few capsules fell. On the ground, unopened and lightweight, they are ready to be carried into the river the next time the water rises after a heavy rain (or after melting snow). At least some of these seeds will likely end up a long way from the parent teee.

One capsule fell into the river and immediately began to float downstream.

Plant seed dispersal occurs in a variety of ways in addition to simply falling (dispersal by gravity). Wind dispersal is common; cottonwood and milkweed are two examples. Dispersal by animals is probably even more common; nuts are carried away and buried and the seeds of fruit that is eaten by birds often pass through their intestines and dropped quite far from the fruit source.

Bladdernut is a good example of seed dispersal by water. It would be fascinating to know how far the bladdernut seeds I was observing this week will travel before spring.

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