That flowers drop after pollenation is caused by self incompetability, which means that the pollinia are rejected by stigmatic surface. Because inflorescence costs a lot of energy it is best to drop the flower because its purpose is served (although unsuccesfully). The same can be seen in interspecific or intergeneric crosses; the pollen is simply not recognized by the female parts so flowers drop.
Also vegetatively propagated plants, for instance your kingianum, can act the same. But it might aswel be succesful. And with kingianum baring lots of flowers why not give it a try. And yes you will see lots of inbred in your seedlings, but you will also find beautiful and strong plants.
Enjoy!
Posted via Mobile Device