These were found in a park in Pittsburgh, PA. From a distance they looked almost like plums, but they're actually hollow, paper-like covers that contain a hard pea-sized seed.

enter image description here

  • $\begingroup$ Thanks for the good description of the fruit, but could you also give an approximate size? And was it a tree or a shrub that you found them on? $\endgroup$
    – RHA
    Aug 5, 2017 at 21:27
  • $\begingroup$ Thanks for your edit in astronomy but I could use all your up votes $\endgroup$
    – Muze
    Feb 7, 2018 at 3:05

2 Answers 2


Most likely a member of the genus Staphylea. Since you are in Pittsburgh, PA, it's most likely Staphylea trifolia L., or an introduced species.

  • $\begingroup$ That is it! I've never heard of (or seen) a "bladdernut" before. $\endgroup$ Aug 8, 2017 at 13:48

By the looks Of it,it mostly is a hop hornbeam Which are indeed found in pittsburgh
But i Still cant confirm it because they are no photos of their leaves and any twigs or the whole tree, this info would be great to identify it and do you mind mentioning the name of the park you've been to
Can you confirm whether the tree looked like this
Ostrya virginis
Ostrya Virginis

  • $\begingroup$ Nope, definetly not an Ostrya species. $\endgroup$
    – aae
    Aug 8, 2017 at 6:28

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