- You Will Get 300 Seeds Of Fireweed / Rosebay (Great Willowherb) Epilobium Angustifolium Flower Seeds. - Description: - Name: Fireweed. - Other Common Names: Rosebay / Great Willowherb. - Scientific Name: Epilobium Angustifolium. - Color: Pink. - Plant Seeds: Outdoors After Frost / Indoors Weeks Before Last Frost. - Plant Height: 36 - 72". - Plant Spacing: 18 - 24". - Bloom Time: Summer. - Hardiness Zone: 2 – 9. - Light Requirements: Sun - Part Shade. - Soil & Water Preferences: Average.