I'm not too sure about any of the morning glory families, but I've haven't heard of any inter-specific hybrids of them... yet. Could it be possible that there are other morning glories around the neighboorhood where a bee may carry the pollen to your plant? Save the seed, just in case.

Hi,

There are several ipomoea interspecific hybrids in fact, although I have not found any one place that has a record of them. Imperialis (=nil) is perhaps one of the more familiar hybrids. Quamoclit when crossed with coccinea yields multifida (=sloteri). Whether the species quamoclit can hybridize with tricolor 'Heavenly Blue', perhaps someone else can tell....

There was probably a busy bee who had visited another morning glory in the neighborhood. I. quamoclit was crossed with coccinea, but only after hundreds of attempts yielded something like 3 seeds. The interspecific hybrid and its seedlings also had intermediate foliage (devided, but not ferny), so if your pink and red seedling has normal foliage, your Heavenly Blue was likely crossed with another morning glory down the street. If you made sure it selfed, you should have a nice mix in the next generation

The story that Agrinerd refers to is in fact a fascinating one. Multifida (=sloteri) is a chance hybrid that was recreated in the lab by crossing quamoclit and coccinea, two species with different chromosome counts. Only a few seedlings resulted, intermediate in plant habit between the two parents. These were infertile in back-crossing to either parent, but did self occasionally primarily by, due to a trick of genetics, doubling its unusual chromosome number from 29 to 58. The selfings became more fertile with each generation. These were more robust than the original F1 hybrids, and exhibited a distinctly different plant habit.

Back to the original question: Taxonomically, Quamoclit and coccinea are very closely related, being in the same string of subcategories of genus Ipomoea, subgenus Quamoclit, section Mina. Heavenly Blue is more distantly related in the line Ipomoea, subgenus Quamoclit, section Tricolores. I know of no ipomoea hybrids where the parents are not of the same section (e.g., Mina); they usually are of the same (finer) subcategory called a series. [The section Mina currently is not divided into series.] So, belonging to different sections, a cross between quamoclit and tricolor 'Heavenly Blue' would seem unlikely to occur.