- You Will Get 20 Seeds Of White Worled (Horesetail) Milkweed Asclepias Verticillata Flower Seeds. - Description: - Name: Whorled Milkweed. - Other Common Names: Horsetail Milkweed / Eastern White Milkweed / Butterfly Weed / Butterfly Milkweed. - Scientific Name: Asclepias Verticillata. - Color: White. - Plant Seeds: Fall / Cold Stratify 2-3 Months. - Plant Height: 24 - 36". - Plant Spacing: 24 - 36". - Bloom Time: Summer. - Hardiness Zone: 3 – 9. - Light Requirements: Sun - Part Shade. - Soil & Water Preferences: Average – Dry.