150 days maturity after transplanting. Allium cepa. Imai Early Yellow Onion Seeds. Non-GMO, cool-season, annual, heirloom. This selection of Senshu Yellow matures 10-15 days earlier than original Imai. A medium-day length, over-wintering variety, it does best in Zones 5 and 6. Maturing to over 8 ounces, the large, yellow-skinned, thick, flat globe bulbs are crisp and mild. Utilize any part of this plant for its onion flavor. Bulb begins to flatten at 13-hour day length. ~ 7,500 seeds / oz.