I discovered ripe seeds on white Pentas this afternoon. I had never been able to save Pentas seeds before; these saved themselves, fine as dust. Dead-heading, I cut the bone-dry seed head holding it in my hand and the tiniest seeds I've ever seen stuck to my finger. What I always thought were seeds were actually pods. I always gathered them before they dried completely and the seeds never appeared because the pods never opened.
In the past, I read every post I could find about Pentas seeds and the description of the seeds were always rather vague. I didn't expect to find seeds even tinier than petunias and nicotiana, but they are. Your breath would blow them away.
I usually deadhead pentas and save some cuttings for the winter. They don't always work out, the cuttings, because the plants hate cool soil and it's cheaper to buy a new plant in spring than to use heat mats. Here are last year's Pentas cuttings, in October.
The plants are iffy perennials outside here. Sometimes they return, sometimes not. I've lost the bright red Ruby, but had plenty of the bold dark pink and some of the other pinks this year. The seeds were on the white Pentas which is new to the garden this year. Away from the others, it missed deadheading a time or two.
Butterflies are attracted to the clusters of star-like blossoms throughout the summer.
I may never grow Pentas from seed, but I have the satisfaction of actually having seen and gathered the tiny seeds.