Lupinus polyphyllus (Large-leaved Lupine)

Type: Perennial
Hardiness Zones: USDA 3–8
Height: 2–4 ft (60–120 cm)
Bloom Time: Late spring to early summer
Sunlight: Full sun to partial shade
Soil: Well-drained, slightly acidic to neutral

Seed Treatment

  1. Scarification:
    • Lightly nick the seed coat with a nail file or knife.
    • Or soak seeds in warm (not boiling) water for 12–24 hours

  2. Cold Stratification:
    • Wrap soaked seeds in a moist paper towel, seal in a plastic bag, and refrigerate for 14 days to simulate winter conditions.
    • Check weekly: If seedlings sprout in the fridge, remove them gently and plant immediately.

Sowing Instructions

When to Sow:

  • Indoors: Start 4–6 weeks before the last frost.
  • Outdoors: Sow in early spring or late fall (for natural cold stratification).

How to Sow:

  • Sow seeds 1/4–1/2 inch (0.6–1.2 cm) deep in well-draining soil.
  • Space plants 12–18 inches (30–45 cm) apart.
  • Keep the soil consistently moist during germination.

Temperature:

  • Ideal soil temperature: 60–70°F (15–21°C).

Germination Time:

  • Germination usually takes 14–30 days, but may take up to 42 days.
  • Be patient—germination may be uneven.

Care Tips

  • Watering: Moderate; water regularly until established.
  • Fertilizer: Generally not needed—lupines enrich the soil with nitrogen.
  • Staking: May be helpful in windy or exposed locations.
  • Deadheading: Encourages prolonged blooming and reduces self-seeding.
  • Transplanting: Lupines dislike root disturbance; sow directly when possible.