- You Will Get 20 Seeds Of Green Spider Milkweed Asclepias Viridis White Purple Monarch Flower Seeds. - Description: - Name: Spider Milkweed. - Other Common Names: Green Milkweed / Green Antelopehorn. - Scientific Name: Asclepias Viridis. - Color: Green - White With Purple. - Plant Seeds: Fall Sow Seeds Or Cold Stratify. - Bloom Time: May – Aug. - Hardiness Zone: 5 – 9. - Plant Height: 12 - 18". - Plant Spacing: 18 - 24". - Light Requirements: Sun. - Soil & Water Preferences: Average – Dry.