Thunbergia is a very easy to grow annual as a climbing vine or in window boxes and hanging baskets. If allowed to climb it will quickly cover a trellis or fence offering a colorful display all summer long.
Other names: Black-Eyed-Susan Vine, Blackeyed Susan Plant
Genus: Thunbergia
Family: Acanthaceae; also placed in Thunbergiaceae
Type: Annual
Thunbergia as a House Plant
Thunbergia are fun flowering house plants because of their versatility. They can be grown in a hanging basket, in an indoor window box, up around a window or on a trellis in a window. Thunbergia is a climber with long, thin tendrils that will grab onto anything they can – including shade pulls, mini blinds, and other plants. Hanging baskets should be given enough clearance to allow the plant to hang rather than attach itself to whatever is nearby.
Thunbergia prefer a moist well drained soil and can also be grown hydroponically or semi-hydroponically. They like sun but will bloom freely if grown in partial sun, such as in a window with an Eastern-exposure.
Types of Thunbergia
Thunbergia come in many varieties, both with and without the dark center ‘eye.’ The most popular variety is Thunbergia alata ‘‘Susie’ (Black-Eyed Susan)’ which is a mix of apricot, yellow and ivory flowers with dark centers. Newer varieties such as Thunbergia alata ‘Spanish Eyes‘ and Thun. alata ‘African Sunset‘ show pastel blends including shades of orange, pink, rose and burgundy. Thunbergia are fairly easy to hybridize and new color combinations debut every spring.
How to Sow Thunbergia Seeds
Thunbergia seeds are easy to germinate. Pre-soaking the seeds overnight will hasten germination but is not necessary. Seeds will germinate in 7 to 21 days and flowering takes anywhere from 6 to 9 weeks depending upon pot size. Being root-bound or pot-bound hastens flowering.
Sow seeds at room temperature (70-75F) in a bright window or under lights using a light potting soil, seed starting mix or mix of perlite and vermiculite. Space seeds 1-2 inches apart and cover lightly with soil or mix. Pre-moistened peat plugs or Jiffy® pellets also work well, just drop the seed into the pre-drilled holes.
Some people prefer to use a heated germination mat and/or propagation dome but neither are necessary for successful germination of thunbergia under normal household conditions. If sowing seeds for outdoor plants sow in early spring and slowly acclimate to outdoor conditions for two weeks before transplanting outdoors (after all risk of frost). For house plants seeds can be sown at any time of year.