Why Black-Eyed Susan Vine Drops Flowers: Cold Nights and Pests

Eva in Seattle bought a black-eyed Susan vine (Thunbergia) two weeks ago. It dropped 3–4 healthy flowers each evening. Balcony pot, PM sun (70–80°F day, 53°F night), watered every 3–4 days, no fertilizer.

Likely Causes

1. Insects: Aphids, whiteflies, mites. Spray soapy water, horticultural soap, or neem oil (check leaf undersides).
2. Overwatering: Test with a stick deep in the pot—soil may feel dry but be wet below.
3. Cold nights: 53°F is too cold for this tender vine. Most important factor.