Black-eyed Susans (Thunbergia alata) are such vigorous growers that you can easily start them from scratch at home. In just a few weeks, a tiny seed transforms into a stunning, lush climbing vine. Here’s how to give your seeds the best start possible.
Seeds and Timing
You can easily collect seeds from an existing plant or pick up a packet at your local garden center. They look a bit like wrinkled peppercorns, though they’re a little flatter. Since Black-eyed Susans aren’t frost-hardy but need a long season to show off those iconic blooms, you’ll want to start them indoors early—February or March is usually the sweet spot.
Soil and Containers
To encourage strong root growth, use a “lean” soil—a standard seed-starting mix is perfect for this. Choose pots that are at least 4 inches (10 cm) in diameter so you have room for a few seeds per pot. Plastic or terracotta both work fine, as long as they have drainage holes. It’s also a big help if your containers have a clear lid or can be easily covered with plastic wrap to hold in moisture.
How to Sow Your Seeds
- Fill each pot with seed-starting mix, leaving about an inch of space at the top.
- Sow several seeds per pot, keeping them a couple of inches apart.
- Cover them with about half an inch of soil, then gently press down with your fingers or a flat tool to ensure good contact.
- Mist the soil thoroughly with a spray bottle.
- Cover the pots with a lid or plastic wrap to keep the humidity up.
- Place them in a bright spot that stays around 68°F (20°C).
Pricking Out Seedlings
Be patient! Germination can take up to three weeks. Once your seedlings have developed two pairs of leaves, it’s time to “prick them out” and move them to their own pots. Pro tip: Plant three seedlings together in one pot. This ensures your vine looks full and lush rather than thin and leggy later on.
Quick Tip:
Regularly pinch off the tips of the shoots. This encourages the young plants to branch out and get nice and bushy right from the start.
Ongoing Care
The propagation journey moves outdoors in mid-May. Wait until the danger of frost has completely passed before moving your babies to the balcony or garden bed.
- Choose a location with full sun, plenty of warmth, and protection from the wind.
- Provide a trellis or support for climbing.
- Keep the watering consistent.
- Use a fertilizer every two weeks during the growing season.
- Bring them indoors in the fall if you want to try overwintering them.
