South facing , in front of a window,someone said I should not use fertilizer
That is true. They don't need fertilizer and they prefer average to poor soil.
These two articles will help you determine what you need to do:
https://www.gardeningknowhow.com/ornamental/vines/morning-glory/morning-glory-not-blooming.htm
https://www.gardeningknowhow.com/ornamental/vines/morning-glory/prune-morning-glory-plants.htm
I have checked that the conditions seem to be right, but no flowers have opened yet on the morning glories.
This article should pinpoint the issue for you:
https://www.gardeningknowhow.com/ornamental/vines/morning-glory/morning-glory-not-blooming.htm
I am told that I should cut the plant down to about 6” above ground and cover with mulch in Texas. My plant is about 8’ tall with branches. Please help before I kill the plant
Yes, that is what our experts say. Here's an article that suggests that exact thing: https://www.gardeningknowhow.com/ornamental/vines/morning-glory/prune-morning-glory-plants.htm
This will sound mystical and a little creepy, but when our cat died, who was beloved by the entire neighborhood, we buried him under his favorite bench in our garden. That night at 10pm I went outside to say goodnight one last time, and the morning glories covering our fence next to the bench were in full bloom. I called others to come and look because I thought I was nuts. I no longer recall if there was a full moon that night, but if there was, could that be the explanation?
Could you have the lavender moon vine? It will bloom at night but you would have noticed that before. I have seen some references that morning glories don't wait till morning to open, they open at dawn. Maybe like you said, a full moon inspired them to open sooner. Whatever the reason, it is very cool and otherworldly, plus I'm sure it was comforting. Just enjoy the story to tell.
https://garden.org/plants/view/122254/Lavender-Moonvine-Ipomoea-muricata/
https://aggie-horticulture.tamu.edu/newsletters/hortupdate/2008/apr08/MornGl.html
I want to plant morning glory vine and use a trellis for the vines; will be kept on the driveway.
I would suggest that you make sure your soil is well-draining, although it does not need to be highly nutritious. Morning glories are not fussy about soil. Make sure your planter has drainage holes. Plastic pots do better through the winter, as clay or pottery tend to break.
https://www.gardeningknowhow.com/ornamental/vines/morning-glory/growing-morning-glories.htm
https://www.gardeningknowhow.com/special/containers/choosing-containers-for-potted-environments.htm
I have been planting morning glories out side my house for years now, each winter I take the seed possible and replant for the following spring. This year almost all of the seeds I have been replanting are all white seeds. 1 pod out of 30 are black seeds. Why? Will they replant and grow like normal?
Mature morning glory seeds are usually brown/black with a hard seed coat. However, some varieties have beige seeds which reproduce just fine. You didn't say if you planted more than one variety. To be sure of plenty of flowers, you may want to supplement with some newly purchased seeds.
https://www.gardeningknowhow.com/ornamental/vines/morning-glory/collecting-morning-glory-seeds.htm
I grew them from seed and they climb on a metal trellis. The summers here are very hot and I was thinking it was too much sun. I feed with Shultz Plus 10-15-10 in water when I water once a week. I water till it begins to drain through the holes in the big pot. The leaves start to wilt in the strong sun. I really do want to grow these, but I need help with this problem. I don't have a picture as we pulled them and hope to start over.
This is normal morning glory behavior. The blossoms open in the morning and drop by evening time. On cloudy days they may not open at all. It's the nature of the plant. It sounds like you're taking good care of the plant. I would water more though if the leaves are wilting and the sun is hot.
https://www.gardeningknowhow.com/ornamental/vines/morning-glory/growing-morning-glories.htm