How to save petunia seeds?

Hi everyone, I was just wondering if I could collect some seeds from my petunia plants? I've managed to figure out how to take seeds from lupins & sweet william all by myself :D but when it comes to petunias I can't spot any obvious seeds, any advice welcome.

 

Not sure many actually bear seed these days.I think they are sterile.

A lot of the big flowering kinds that completely fill a pot are grown from cuttings each year I believe.
Being sterile means they continue to flower all summer.

There are a few of the seed grown types around and the seed pods are fairly obvious, they just need to become brown on the plant before picking.

 

Seeds from Petunias will be the same as anything else.
The first thing is you have to see the seeds.
Now that you mention it, I don't think I have ever seen seeds on Petunias.
What other plants do gardeners never see seeds on ?