Morning Glory colour change


Does the colour of morning glories change according to the soil chemistry, as some hydrangeas do?

For years I’ve planted morning glories against the wall in my front garden (I’m in Toronto). I love the big Heavenly Blue ones. I buy a new seed packet every year from a garden shop, and put the seeds in the ground once frost is over, so i grow the plants from scratch.

The past three years, although i’ve bought Heavenly Blue seeds, my morning glories bloomed purple, and with smaller flowers than the blue. I thought it must be a mix-up with seeds (unlikely for 3 consecutive years, but still….) except that this year, i put a couple of my new seedlings against the fence in my back yard, and lo and behold, they bloomed blue! So I am getting some blue and some purple plants from the same seed packet.

Wondering how to explain this. Is it the soil? Fertilizer? Too dry or wet? Something else I am doing, or not doing? I’d love to reinstate the blue flowers in my front garden!

Thanks for advice.


Thank you for contacting the Toronto Master Gardeners.

The colour of the morning glories is due to anthocyanins which change  with the pH. As a result, with normal fluctuations in pH levels, its petals can shift in color from blue to pink, and sometimes red in the course of a single day.

The following two articles deal with the colour change of Ipomea (morning glory) petals between flower opening.: