 Trillium grandiflorum is a perennial that grows from a short rhizome and produces a single , showy white flower atop a whorl of three leaves . These leaves are ovate ( i.e. , egg @-@ shaped ) in outline with pointed tips . They lack petioles ( or have extremely short ones ) and measure 12 – 20 cm long by 8 – 15 cm wide ( 5 @-@ 8 in long by 3 – 6 in width ) , with very prominently engraved venation . The leaves and the stem share a dark green color and persist into autumn . Leaves and petals both have somewhat undulate margins , the leaves often much more strongly so . Individuals grow to between about 15 and 30 cm tall ( 6 – 12 inches ) . A single rootstock will often form clonal colonies , which can become very large and dense . 
