I have a passion vine that has never produced fruit, yet I have new vines growing all over my yard.

Question

yard. Can they propagate from seeds dropped from flowers?

Answer 1

No, in order to produce seeds it has to flower and fruit completely. The fruit is what holds seeds. If it doesn't fruit, then you could be lacking potassium, and possibly phosphorus. If you have flowers, though, then it is just likely a potassium deficiency.

This can also happen if there is too much nitrogen in the soil, in which case it can be fixed, also, by adding phosphorus and potassium.

https://www.gardeningknowhow.com/ornamental/vines/passion-flower/passion-flower-not-fruiting.htm