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.
