Ok, I am going to admit my ignorance ! For a few years I have collect cuphea "seeds" from my batface cuphea. However, they didn't germinate. Hmmm, is something wrong here?
I was out in the middle of my 4 rather large cupheas just looking at them (actually looking for limbs with little roots where they touched the ground). I accidentally discovered the split pods on the cupheas !! The brown seeds were hanging out,ready to drop. I had been collecting the "pods" (dried flowers) after they were completely brown. But these were still green! I took them inside and the seeds almost fell out on their own.
It depends on how the weather is. If it's very warm, a part of the seeds will turn brown and will hanging out, but the other ones in the pod will still be green. If weather is not so warm they ripe better. Well, at least in my zone 6.
And I was very surprised to have hundreds of seedlings this year. I removed them, because I wanted to grow another Cuphea this year, but they kept coming up, so finally I gave up and gave them the freedom to grow after I harvested seeds of the other Cuphea.
If you want to germinate Cuphea seeds indoors , just cover them very thiny and only use the brown ones.
I never had problems growing any Cuphea as long as the seeds were brown.
And to stephanietx
The pods are indeed sticky. Sometimes I think it's a plant that eats insects, because I find a lot of insects that sticked to the pods. If one wants to collect insects, this is a great plant to do.