"Jumpseed" was long known as Tovara virginiana. It is now called Polygonum virginianum or Antenoron virginianum. It is common in forests in Indiana, and when the fruits are dry, if you grasp the stem between thumb and forefinger and slide slowly upward, the seeds will "jump" away from the plant quite some distance. It is also known as Virginia Knotweed or Woodland Knotweed, but don't be fooled by the name - it is native here.
