Milk Thistle (Silybum marianum) Seeds

Milk Thistle (Silybum marianum) is a bold biennial plant admired for its vivid purple flowers and distinctive glossy leaves marbled with white veining. Its towering stature and spiny bracts make it a dramatic focal point in ornamental borders, wildlife gardens, and naturalized meadows. Nectar-rich blooms support pollinators, including bees and butterflies, while its unique foliage adds textural contrast to sunny, dry landscapes.

Features

• Dramatic purple blooms with striking spiny bracts.
• Variegated white-veined leaves add bold texture to gardens.
• Excellent pollinator plant that supports bees and butterflies.
• Drought tolerant once established; thrives in full sun.
• Non-GMO Silybum marianum seed variety.
• Strong architectural plant great for borders and wild landscapes.

Specifications

• Common Name: Milk Thistle
• Scientific Name: Silybum marianum
• Plant Type: Biennial flowering herb (sometimes annual in hot climates)
• USDA Zones: 4–9
• Bloom Color: Purple-magenta with spiny bracts
• Foliage: Glossy green with white marbling
• Height: 48–60 inches
• Spread: 18–36 inches
• Growth Habit: Upright, branching, spiny foliage and flower heads
• Heirloom: Yes
• GMO Status: Non-GMO
• Organic: Not certified organic
• Light Requirements: Full sun
• Soil Preference: Well-drained soil; tolerates poor, rocky ground
• Water Needs: Low once established
• Drought Tolerance: High
• Pollinator Friendly: Yes (bees, butterflies)
• Maintenance Level: Low
• Plant Spacing: 18–24 inches
• Seed Viability: 2–3 years stored cool & dry

Planting Guide

• Direct sow in spring or fall for best results; can also start indoors 4–6 weeks before frost.
• Lightly scarify seeds (nick or rub with sandpaper) to improve germination.
• Sow 1/4 inch deep in well-drained soil and water lightly.
• Expect germination in 10–20 days in warm conditions.
• Transplant or thin seedlings to 18–24 inches apart.
• Provide full sun for compact form and vivid foliage.
• Water sparingly once established; avoid overwatering.
• Allow flowers to dry on the plant if reseeding or wildlife interest is desired.
• Remove spent flower stalks to control spread in cultivated beds.