When my Utricularia nelumbifolia produced a flower stem, I had a problem: How do I properly pollinate the flower to obtain seeds? Since I did not find anything about the pollination of Utricularia on the Internet, I decided to write a small article for my homepage. Here I try to explain how to pollinate a flower using U. nelumbifolia as an example:

When the flower is fully open, you can start. To do so, open the flower and pick up the pollen with a very fine brush. You can also use a black colored toothpick (this makes it easier to see whether you have "caught" pollen). Now use the pollen to brush the flower stigma (see arrow!). I'm not really sure, but in my opinion the stigma or the little "lid" closed afterwards. If, by the way, you are not afraid of damaging the flower, you can simply peel off the corolla beforehand and easily dust the pistil / stigma.
After successful pollination, the flower will fall off within the next few days, unless you have already removed it.

The seed capsule then begins to ripen slowly. If it bursts open and the seed pod slowly resembles parchment (after about 4 weeks), you can harvest the seeds. You shouldn't take too much time with it, because the seeds are not long-lasting and lose their ability to germinate or rot very quickly (especially with U. nelumbifolia and U. humboldtii ) , but the seeds of some species remain germinable for a few years.
If you look at the seeds of this type under the microscope, you can already see the green "seedling".

Now you can sow the seeds on a suitable substrate (sphagnum or peat-sand mixture). I even put a few seeds in the water of the pot. What is special about U. nelumbifolia seeds is that they germinate within a few hours. You can almost watch them germinate. The germination rate was almost 100 percent for me. Armed with a camera and a tripod, you can also produce a nice series of pictures.