Question
Hello Kathleen,

I just bought a black-eyed susan vine  2 weeks ago. Repotted it.
Problem: In the evenings it would drop 3-4 healthy, whole , nicely blooming flowers. What   am I doing wrong? What should I do to prevent loosing them ?

The plant is on my balcony in a pot  , gets PM sun ( 7o-8o F these days, night time 53 F), water it every 3-4 days ( instruction tells me once a week, but I felt dry to the touch), no fertilizer (yet).

What would be your suggestion ?

Thank you :
Eva

Answer
Good day, Eva!
I am happy you have chosen one of my favorite flowering vines. Generally, Black-Eyed Susan vine (Thunbergia) likes morning sun and p.m. shade, but they are probably just as happy with the reverse, as long as they do get 5-6 hours of direct sun each day.  Bloom drop is likely due to one of two things: (1) root disturbance or (2) the plant needs a bit of fertilizer.
Since you've only had the plant for a few weeks, and because you repotted it, I am betting that it's the former. Thunbergia are tough, but they do get mad when their roots are disturbed. Once they've settled into their new pot, though, they will bounce back and start blooming reliably again.  That said, they do like a complete fertilizer every 5-6 weeks or so. Look for a 10-10-10 fertilizer - just make sure the bag or box has equal numbers for the three main components of fertilizer (nitrogen, potassium, and phosphorus). Good luck, hang in there, I don't think you should worry too much. As for watering, as long as it has good drainage and you are waiting to water when the soil is dry down to one inch when you put your finger in the dirt, you're good to go. Let me know how everything goes!