Calla palustris (Bog Arum, Marsh Calla, Wild Calla, Water Arum)

Seed Treatment:
Warm-to-cold stratification is required for successful germination.
• Start by maintaining a warm period at 71°F (22°C) for 2–4 weeks.
• Then, cold stratify seeds at 32°F (0°C) for 4–6 weeks.
• It is okay if the water freezes during cold stratification — this mimics natural overwintering conditions.
• After stratification, allow temperatures to rise gradually to promote germination.

When to Sow:
Indoors: Begin stratification process in late winter to prepare seedlings for spring planting.
Outdoors: Sow in fall or early winter if natural cold stratification is preferred (in cold climates).

Sowing Instructions:
• Use waterproof plastic trays or containers without drainage.
• Fill trays with nutrient-rich, muddy soil (such as loamy compost mixed with water).
Sow seeds on the surface and press gently into the mud.
• Keep approximately 0.4 inches (1 cm) of water above the soil at all times.
• After stratification, maintain moist conditions and moderate temperatures for germination.
• Germination may occur in 4–8 weeks after the stratification period, though it can be erratic.

Light Requirements:
• Prefers partial shade to full sun, depending on climate.
• In warmer zones, partial shade is ideal to prevent overheating.

Soil Requirements:
• Needs nutrient-rich, saturated or muddy soil.
• Suitable for bogs, pond edges, and consistently wet areas.
• pH range: 5.5–7.0 (slightly acidic to neutral).

Watering:
• Keep soil continuously wet or submerged in shallow water.
• Do not allow soil to dry out at any stage.

Spacing:
• Transplant seedlings 8–12 inches (20–30 cm) apart once large enough to handle.

Growing Tips:
• Grows as a rhizomatous perennial, producing heart-shaped leaves and white spathes in spring to early summer.
• Ideal for pond margins, rain gardens, and marshy beds.
• Hardy in USDA Zones 3–7.
• May spread by rhizomes in favorable conditions—can be gently divided if needed.