Question
QUESTION: We had some full grown vinca last year.  Some of them re seeded this year with no help from us.  How did this happen?  I know some of them replanted since we planted different plants this year.  We really love the vinca and want to know what happened during the fall/winter that brought some of them back.  Thanks

ANSWER:  Vinca grows readily from pieces and these will be exactly like the mother plant. The mature plant produces seed pods. These seeds will germinate and grow when conditions are right. Do not expect these seedlings to have the exceptional feature(s) of the mother plant.

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QUESTION: Thank you,

So should we pull up the vinca after the 1st frost? Or should we leave the mature plant in the ground so that the seeds on them will germinate for next year?

Answer
There is no guarantee that seedlings will be anything like the mother plant or that germination rate will be high enough to fill the area. If you like even growth and uniform color which are special attractions of annuals, then you are better off installing new plants.