I've yet to have a Heavenly blue reseed, and there's plenty of mulch around for them. In our area, or at least on our street, morning glories, save for the wicked kniola, have to be planted annually.

It may me a little cold to grow Ipomea alba or Moonflower in your zone. Ipomea purpura or Morning Glory will grow up to zone 4.

@Leafhead It gets pretty warm though where I used to put morning glories, too warm in afternoons for the Heavenly blue. I had to baby them w/misting on hot afternoons. Used to plant them for my husband & they would climb up our railings providing a gorgeous screen.

As an aside it was interesting, and AGGRAVATING to see that the kniola would "fight" with them. It's like the two would NOT grow together. What happened was the blues diluted the deep black purple of the kniola next years but the blues would not reseed, leaving me to an unnamed botanical tier in Dante's inferno perpetually yanking kniola. NEVER again. Do NOT plant kniola unless you care to risk never seeing another type of morning glory without a struggle.

@Qualia
Morning Glory isn't at the top of my list for this very reason. I have seen other gardeners pull their hair out over these overtaking monsters. I have also seen MG scale trees and traverse telephone lines!
The only thing I have seen using MG are hummingbirds, and I can easily top MG in that area with some Cardinal Flower and some Salvia.
My advice: keep pulling and plant something there that may be allelopathy to MG. Wild Ginger may do the trick.

@Leafhead Thank you for the tip- very cool. Plant wars!

@Spinliesel Thank you so much! I will be checking the link out later. ((( hugs )))
I've never seen one in person

Oy. That happened when I planted Kniola morning glory one year. They were all "ooooh feel sorry for us we are the delicate goth purple flower, love us" ...then RAWWWWR they're everywhere and they "beat up" the heavenly blues. I've now been fighting kniola for oh... 10 years (I now check EVERYTHING for virulency reviews before planting)

True Moon flower blooms at night

@Leafhead In that case I would say the one I found was just a mutant blue.

@Rugglesby
That's what's known as an alba or white form. Alba are not albino, which is incompatible with life for green plants. They are just pigment deficient