Hibiscus trionum

Hibiscus trionum is an annual plant that is native to the east of the Mediterranean in the Levant. 
It has spread both because people grow it as a garden plant, and because it can grow as a weed. The plant grows to a height of 20-50 cm, sometimes as much as 80 cm, and has white or yellow flowers with a purple centre. Common names for the same plant include bladder hibiscus, bladder ketmia, bladder weed, flower-of-an-hour, flower-of-the-hour, modesty, puarangi, shoofly, and venice mallow.