This particular P. selloum is one that we found out of a large planting in a housing community not far from our facilities. It has some very desirable characteristics, like shorter, thicker petioles and slightly more compact growth than most P. selloum we have seen.
The picture below is an inflorescence on the same plant, shown at the stage just prior to pistil receptivity to pollen. Notice that the spathe has just opened slightly, revealing the spadix within. This shot was taken in the morning, and the evening of that same day (often quite late in the evening!) is, generally speaking, the most auspicious time to pollinate. Air and soil temperature will affect the timing somewhat, and only experience will enable a successful result.