Pollination of tuberous drosera flowers
Of course, before you can grow anything from seeds, you need to get some seeds. How does that work? Once more, there is no simple answer which fits to all species. I start with the easy ones, which do everything for you. You only need to harvest the seeds once they are ripe. That really sounds easy and indeed it is. Here is a list of self-pollinating species offering full service:
Drosera bicolor (some clones but not all)
Drosera bulbosa ssp major (some clones)
Drosera macrantha ssp. planchonii
Drosera ramellosa (at least some of them, some others are self-fertile but they need you to move the pollen onto the anthers)
For the pollination of any other species you will need two genetically different plants (=clones). If such two or more different clones flower the same day, you just need to rub the flowers at each other so that the pollen is transferred to the other flower.
If you do have different clones but they do not flower on the same day, you can harvest the pollen from the earlier flower and store it cool and dry until the second clone starts to flower. Now you can use the store pollen of clone 1 for pollination of clone 2.
If pollination was successful, the seed pod will swell and eventually split open.
Many species will open their flowers only for a few hours and pollination needs to take place during this time. A few species, however, will flower for several days and the length of the flowering time will depend on the outside conditions (temperature, light intensity and probably other factors). Some species like Drosera heterophylla will close their flowers during night and open the flowers again when the light levels are high enough (meaning: not on overcast days), whereas others like Drosera graniticola will keep their flowers open. All of these species seem to start flowering while the anthers are still closed and therefore the pollen is not yet available. The anthers will split open and release the pollen some time after the flower opened. Depending on the conditions it may be after one day or later.
The easiest method to achieve cross pollination of different clones you just need to rub carefully two flowers together. If that is not possible you can use tweezers or other tools to transfer the pollen from one flower to the other.
I tried quite a few hybridizations in the past. Interestingly, you can induce pollination of e.g. Drosera macrantha with Drosera browniana pollen when rubbing both flowers together. The seed pods will swell and you will be able to harvest seeds later on. In that specific example I even observed some germination of seeds harvested from both parent species. Nevertheless, the seedlings were not viable and died shortly after germination. In other cases the seeds did not even germinate.
If you do not remove the pollen sacks form the pollen acceptor flower the transfer of pollen from a different species may only remove the self-pollination barrier and as a consequence you may actually get self-pollination. I observed this twice (with D. moorei and D. menziesii), in both cases the pollen donor was a D. andersoniana.
It seems to be possible to produce hybrids among the Drosera menziesii subspecies. However, those are so far the only successful examples of hybridisation I came up with. Recently, I tried a cross of Drosera whittakeri and Drosera aberrans. Let's see what grows out of those seeds.