Sow the Black-eyed Susan

Harvesting black-eyed Susan seeds

This is not really a viable option! It rarely fruits in our climates that are not warm enough for this beautiful tropical plant to complete its cycle. If you grow it in a warm greenhouse, you may observe the flowers turning into small capsules. In this case, allow the capsule to dry before harvesting the seeds. Do this before the capsule bursts, or you will have difficulty retrieving the seeds scattered far and wide.

You can find Thunbergia seeds available commercially. On our site, several varieties in different colours are offered for sale: Thunbergia alata ‘Superstar Orange’, and Thunbergia alata in a mix of orange, yellow, and white for the classics. Also consider the lovely ‘Salmon Shades’, with cream, apricot, salmon, and orange hues in a beautiful gradient. The charming Thunbergia ‘Blushing Susie’ in red and pink softened with ivory and apricot offers lovely colours that you may prefer if you are not keen on yellow-orange tones. Feel free to mix different black-eyed Susans.

Some varieties of Thunbergia: top left, ‘Sunny Susy Lemon Sunrise’, bottom, ‘alata Orange’, and on the right ‘African Sunset’

Sow black-eyed Susan seeds

Sowing is simple, but it involves several delicate steps on the path to success. It is important to be attentive to carry them out properly.

You can sow in advance in February-March indoors, in pots, or directly in the ground from April in well-warmed soil.

February-March Sowing Indoors:

Proceed in a location with a constant temperature of 18 to 20°C, well-lit and sunny. Prepare a very light mix to encourage germination: equal parts turf and sand. You can also sow in a special seed compost, possibly enriched with a bit of vermiculite.

• Soak the seeds for 24 hours before sowing.
• Sow two to three seeds per pot, positioning the seeds 6 to 10 millimetres deep at most.
• Lightly firm the soil.
• Water gently with a fine spray.
• Monitor your sowing for 14 to 21 days, the time for germination, watering lightly and regularly. The substrate must not be waterlogged, but do not let it dry out for too long.
• Once the young shoots emerge, continue to care for them with the same attention. The shoots are fragile, maintain light and regular watering, along with consistent light and temperature.
• After 3 to 5 weeks, the seedlings are robust enough to be separated and potted into individual pots, still under cover.
• In May, when the soil is well warmed and the risk of frost has passed, plant the young plants in the garden in a warm, sheltered, and sunny position. See below for how to prepare the planting soil if necessary.
• You can also place them in pots or containers of 20 cm in diameter (more for taller varieties) in a substrate made up of equal parts compost, garden soil, and compost.
• Set up a support for the Thunbergia to climb quickly.

April to June Sowing Outdoors:

For those of you in the warmer regions, do not hesitate to sow directly in place, in warmed soil, during the months of April to June, at 15 to 25°C. Choose a sunny location, but protected from the hottest rays of midday. Sow in light, humus-bearing soil. Amend your soil if necessary with compost or seed compost to enrich it. If it is heavy, lighten it with sand and compost. Place 2 or 3 Thunbergia seeds in clusters every 30 cm. Stake them. You can also let them trail on the ground.

Water regularly during the summer heat to support flowering. Do not let the soil or pot substrate dry out.

The various varieties of Black-eyed Susans range from bright yellow to warm orange, including salmon and reddish-brown. If you mix different varieties, you will create beautiful lianas with vibrant colours that always complement each other.

Some varieties are known to be challenging. Stack the odds in your favour by opting for the warmest temperatures, the most light, and sunshine. Once established in the right spot, they are undemanding and generous!

It is not always easy to find the right conditions for sowing, but it is always rewarding to try!