I'm in Minneapolis. For years we've planted and enjoyed Heavenly Blue morning glories (from small plants, not seeds) but in the past three summers, most of the plants (five of six) produced the small purple and pink flowers which aren't what we want. None of the nurseries have an explanation for this situation and I can't see any similar complaints on the web.
Heavenly Blue Morning Glory Produced Pink and Purple Blooms
Certified GKH Gardening Expert
You may want to test your soil. Morning glories like soil pH slightly acidic to slightly alkaline (6.0 to 7.5). Acidic soil (pH below 7) may encourage purple/pink blooms in some plants; alkaline (pH above 7), blue.
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