Eryngium planum (Blue Sea Holly)

Seed Treatment

  1. Cold Stratification:
    • Mix seeds with moist sand or peat moss in a plastic bag.
    • Store in the refrigerator at 35–40°F (1–4°C) for 4–6 weeks.
    • Check regularly to ensure moisture but avoid mold growth.

  2. Scarification:
    • Lightly rub seeds with fine sandpaper or soak in warm water for 12 hours before sowing.

Planting Instructions

  1. Sowing Time:
    • Best sown in late autumn or early spring after stratification.
    • Direct sow outdoors in fall for natural stratification.

  2. Soil Preparation:
    • Prefers well-draining, sandy, or loamy soil.
    • Soil pH: 6.0–7.5 (neutral to slightly acidic or alkaline).
    • Avoid heavy, waterlogged soils.

  3. Sowing Depth & Spacing:
    • Sow seeds ⅛ inch (3 mm) deep on the soil surface and lightly press them down.
    • Space seedlings 12–18 inches (30–45 cm) apart.

  4. Temperature & Light Requirements:
    • Germination temperature: 65–75°F (18–24°C).
    • Requires full sun for best growth and flowering.

  5. Watering:
    • Keep soil moist but not soggy until germination.
    • Once established, Eryngium is drought-tolerant and requires minimal watering.

  6. Germination Time:
    • Seeds take 3–5 weeks to germinate after cold stratification.
    • Some seeds may take several months if conditions are not ideal.

  7. Transplanting:
    • When seedlings develop 2–3 sets of true leaves, transplant them carefully.
    • Avoid disturbing the deep taproot, as Eryngium does not transplant well once mature.

  8. Care After Planting:
    • Requires little maintenance once established.
    • Apply mulch around plants to suppress weeds and retain moisture.
    • Avoid excessive fertilization, as it thrives in nutrient-poor soil.
    • Deadhead spent flowers to encourage more blooms or leave them for ornamental winter interest.

Additional Tip:
Eryngium planum is deer-resistant, attracts pollinators, and makes an excellent cut or dried flower for floral arrangements!