Iris versicolor (blue-flag iris) is a native aquatic plant that grows from Maine to Virginia. It is an important species of wetland regeneration and restoration. Unfortunately, seed germination seldom occurs in the wild. To address this problem, seeds of Iris versicolor were soaked with gibberellin acid (0, 500, 1000, and 1500 ppm) for 24 h after 120 days of cold treatment at 4 °C and then were randomly assigned to three germination temperatures (constant 21 °C; 24 °C/18 °C; 27C/15 °C) and placed in darkness. Germination rates for the three temperature treatments were 54.4% (21 °C), 96.5% (24 °C/18 °C), and 96.0% (27C/15 °C). Oscillating temperature treatments had significantly greater germination rate than constant temperature. Gibberellin acid had significant influence on germination rate; only the constant 21 °C was not favorable for germination. The germination rate was higher at 1000 than at 500 ppm or 1500 ppm or more. Germination occurred within 10 days under germination temperature treatments. All seedlings in petri dishes were successfully transplanted into growing flats.