Thunbergia alata (Black-Eyed Susan Vine)

For optimal germination rates, initiate seed propagation indoors under controlled conditions—unless the species exhibits a high sensitivity to root disturbance. This approach allows precise regulation of temperature, humidity, and light, improving germination consistency and seedling viability. Do not skip any recommended seed treatments, as they are essential for uniform and successful germination.

Keep soil evenly moist during germination. DO NOT LET IT DRY OUT—once seeds begin absorbing water (imbibition), drying can kill the seed embryo, and even brief dryness after sprouting can kill seedlings.

Seed Treatment:
Scarification: Nick or gently rub seeds with sandpaper to help break the seed coat
Soak seeds in warm water for 12–24 hours prior to sowing to improve germination

When to Sow:
Indoors: Start seeds 6–8 weeks before last frost
Outdoors: Sow after the danger of frost has passed and soil is warm (around 60°F / 16°C)

Sowing Instructions:
• Sow seeds ¼ inch (6 mm) deep
• Keep soil evenly moist during germination
• Ideal temperature: Use a heat mat to maintain steady temperatures of 70–75°F (21–24°C)
Humidity: Use a humidity dome or clear cover to maintain consistent moisture during germination. Open the dome BRIEFLY once per day to allow fresh air in and reduce mold risk. Remove the dome entirely once seedlings emerge.
• When seedlings emerge, use grow lights to maintain 14–16 hours of light per day.
• Germination occurs in 10–35 days

Watering:
• Keep soil consistently moist but not soggy
• Water deeply during dry spells once established

Spacing:
• Space plants 12–18 inches (30–45 cm) apart
• Provide a trellis or support for vines to climb

Growing Tips:
• Requires full sun for best flowering
• Can tolerate light afternoon shade, especially in hot climates
• Prefers well-draining, fertile soil
• Add compost to enrich poor soil
• pH range: 6.0–7.5
• Produces bright orange, yellow, or white blooms with a distinctive dark center
• Blooms from mid-summer to fall
• Great for containers, hanging baskets, trellises, and fences
• Grown as an annual in most regions, but may be perennial in USDA Zones 10–11
• Deadhead spent blooms to encourage continued flowering

More guides at: bloomoutlet.com/seed-guides