Wood Poppy's happy yellow flowers bloom in spring on stems stretching up about a foot from the ground. 
 
Also called Celandine Poppy, Wood Poppy is not too aggressive for a garden; it does self-seed but unwanted plants can be pulled easily.  It's native just south of us, from Pennslyvania south and one of my personal faves.  It is listed as endangered in Canada.
 
Try pairing it with Trillium and Jacob's Ladder.  Deadheading after blooming may stimulate more flowers.
 
Fun fact: Stems contain a bright yellow sap which was formerly used as a dye by Native Americans.  
 
Wood Poppy should not be confused with Greater Celandine, Chelidonium majus, an invasive plant from Eurasia.