Hibiscus trionum

from WordNet (r) 3.0 (2006)

Hibiscus trionum
    n 1: annual weedy herb with ephemeral yellow purple-eyed
         flowers; Old World tropics; naturalized as a weed in North
         America [syn: {flower-of-an-hour}, {flowers-of-an-hour},
         {bladder ketmia}, {black-eyed Susan}, {Hibiscus trionum}]

from The Collaborative International Dictionary of English v.0.48

flowers-of-an-hour \flowers-of-an-hour\ n.
   An annual weedy herb ({Hibiscus trionum}) with ephemeral
   yellow purple-eyed flowers, native to the Old World tropics
   and naturalized as a weed in North America.

   Syn: flower-of-an-hour, bladder ketmia, black-eyed Susan,
        {Hibiscus trionum}.
        [WordNet 1.5]