Getting it to bloom

Why won't my Black-eyed Susan vine bloom? (and how to make it flower)

Also called black-eyed Susan vine, clock vine, thunbergia (Thunbergia alata).

More about black-eyed susan vine

About Black-eyed Susan vine

Thunbergia alata · also called black-eyed Susan vine, clock vine · flowering

Black-eyed Susan vine is a tender twining climber from tropical East Africa, grown for its cheerful orange, yellow, or white flowers with dark chocolate throats. A frost-tender perennial usually treated as a summer annual, it blooms from midsummer to autumn on a sunny trellis or in a hanging basket. Not on the ASPCA list; treat as mildly toxic.

Plant type: flowering

Watch for — Few or no flowers: Usually too little sun (needs 6+ hours), an immature plant, or over-feeding with nitrogen. Move to a brighter spot and switch to a high-potassium feed.

The reasons black-eyed susan vine isn't blooming

Almost every non-blooming black-eyed susan vine traces back to one of these, roughly in order of how common they are:

Too little sun — most of these need full sun (or very bright light) to flower well; shade gives leaves, not blooms.
Too much nitrogen feed, driving lush foliage at the expense of flowers (very common with general or lawn feeds).
The plant has not been deadheaded, so it stops flowering once it sets seed.
Irregular watering — drought or waterlogging at the budding stage makes buds abort.
It is still too young or was checked by a transplant and is rebuilding before flowering.

Feeding black-eyed susan vine a high-nitrogen general feed and growing it in too little sun — you get a big leafy plant and almost no flowers.

The fix — how to get black-eyed susan vine to flower

Maximise sun. Give black-eyed susan vine the sunniest spot you have — for most bedding and fruiting plants, more direct light directly means more flowers.
Switch the feed. Move off high-nitrogen feeds and use a higher-potassium "bloom" or tomato-type feed as it comes into flower.
Deadhead regularly. Remove spent flowers often to keep it producing more rather than stopping to set seed.
Water consistently. Keep moisture even through budding and flowering — drought-then-flood swings make buds drop.

Light and feeding do most of the heavy lifting here. Dial in the spot with the light guide for black-eyed susan vine and get the feeding right with the black-eyed susan vine fertilising schedule — the wrong feed (too much nitrogen) is one of the most common silent reasons a healthy plant makes leaves instead of flowers.

Bloom season and what to expect

Black-eyed Susan vine flowers across its growing season (mostly summer) and, kept fed and deadheaded, can bloom for many weeks or right up to frost.

Post-bloom care so it flowers again

Deadhead, keep feeding lightly, and many will rebloom; collect seed from the best plants at the end of the season if you want to grow them again.

For everything else this plant needs day to day, see the full black-eyed susan vine care brief and its watering schedule — a stressed, badly watered plant rarely has the energy to flower at all.

Black-eyed Susan vine blooming — frequently asked questions

Why won't my black-eyed susan vine flower?

Black-eyed Susan vine blooms on the season's growth given enough sun, warmth and the right feed — there is no cold or photoperiod trick, just good growing conditions and a bloom-leaning feed. The most common reason it is not happening: Too little sun — most of these need full sun (or very bright light) to flower well; shade gives leaves, not blooms.

How do I make black-eyed susan vine bloom?

Give black-eyed susan vine the sunniest spot you have — for most bedding and fruiting plants, more direct light directly means more flowers. Move off high-nitrogen feeds and use a higher-potassium "bloom" or tomato-type feed as it comes into flower.

When does black-eyed susan vine normally bloom?