The periwinkle has little seed pods, they will ripen and fall everywhere... They start out green and turn brown... and impatiens have a different little pod it will explode when touched, much like the flower Touch Me Nots... My impatiens are just starting to get the seed pods, I'm in zone 8B...

In the posting the statement was made, "periwinkle has little seed pods" but I see no pods. Are they located at the base of the flowers or do they grow somewhere else on the plant? I see no pods on mine that I can identify.

Hi,
You might not be seeing any seed pods because there might not be any there. Sometimes plants don't make seeds because the flower was not pollinated. This can happen because of the weather like if it is above a certain temperature or because of low pollinator activity. There are a few sterile hybrids so they don't make seeds at all.
The pods would be at the base of where the flower was.

The link below has pics of a couple types of impatiens pods.
Remy

Here is a link that might be useful: The Seed Site Page w/Impatiens