Despite what the AHS database says, going by its hybridizing behavior, STARRY DAY is a diploid, not a tetraploid. This was determined many years ago by various members of the snail mail polytepal (as the term was back then) round robins. I personally have confirmed this for myself, by various crosses against known diploids. (I still have a polymerous seedling which I have kept for many years, whose parentage involved STARRY DAY, and also the diploids SPARKLING OPAL and FOUR STAR.)

To compound and propagate the error, If you look at the three child plants listed for STARRY DAY, all of THOSE are also (imho) incorrectly registered as tetraploids. If you look at the other parents involved in the crosses - GIVE ME EIGHT, PURPLE PETALOID, FUCHSIA FOUR - those are all definitely diploid.

STARRY DAY's hybridizing behavior has been known for many, many years. I am surprised that its designation as "tetraploid" still persists in the AHS database - and now is unfortunately being propagated in this database.