Mexican Butterfly Weed

40 Seeds

Seeding Mexican Butterfly Weed (Asclepias curassavica) — also known as Tropical Milkweed — is a fantastic way to support pollinators like monarch butterflies, bees, and hummingbirds. This tropical milkweed is a fast-growing, heat-loving perennial in warm zones (9–11) and is typically grown as an annual in cooler climates.

Here's your full growing guide:

🦋 Mexican Butterfly Weed (Asclepias curassavica) – Seeding Guide

📅 When to Sow

Indoors (recommended):

• Start seeds 8–10 weeks before last frost

  • Example: Sow in late February to March for a May transplant

Outdoors (optional):

• Sow after last frost, but only in warm climates with a long season
  (Direct sowing may delay bloom significantly)

🌱 How to Sow

Seed Prep (important):

• Scarify seeds lightly (rub gently with sandpaper or nick with a nail file)

• Soak in warm water for 12–24 hours before sowing
  → This improves germination by softening the seed coat

Sowing Depth & Soil

• Depth: Sow seeds ¼ inch (6 mm) deep

• Use well-draining seed-starting mix

Light: Moderate to bright indirect light during germination

🌡️ Germination

• Temperature: 70–80°F (21–27°C)

• Time: 10–21 days

• Germination can be slow and uneven — keep soil consistently moist, not soggy

🌿 After Germination

• Transplant seedlings when they have 2–3 sets of true leaves

• Harden off for 7–10 days before planting outdoors

🌞 Transplanting Outdoors

• After last frost and when nights stay above 50°F (10°C)

• Sun: Full sun (6–8+ hrs/day)

• Soil: Well-draining, average to sandy soil

• Spacing: 12–18 inches apart

🌸 Blooming

• Blooms 90–100 days from sowing

• Produces bright red and orange umbels throughout summer and fall

• Flowers attract monarchs, hummingbirds, bees, and more

🪴 Maintenance

• Deadhead spent blooms to encourage more flowering

• Can be pinched to promote bushier growth

• Water moderately; tolerates drought once established

• In frost-free zones, cut back yearly to reduce disease pressure

⚠️ Ecological Note (Important!)

• In tropical and subtropical areas (zones 9–11), cut back plants at least once a year to prevent:

  • Year-round monarch breeding (which can spread OE parasite)

  • Interruption of monarch migration cycles