Poorly Performing Hummingbird Trumpet Vine.

Question

Planted it 20 years ago. Never flowered for 15 years, had a few flowers. This year only one. No succession. It obviously doesn’t like its conditions. Gets part sun part shade.

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Answer 1

It's probably lack of sunlight. Also, they like poor soils, so if you fertilize, it may be getting too much nitrogen. Here is more:

https://www.gardeningknowhow.com/ornamental/vines/trumpet-vine/trumpet-vine-no-blooms.htm
https://www.gardeningknowhow.com/ornamental/vines/trumpet-vine/growing-trumpet-vines.htm