The Japanese morning glories can be grouped into two sorts: those which are derived only from Ipomoea nil, and those which are hybrids of Ipomoea nil and I. purpurea. The Ipomoea nil sorts have been grown in western gardens for well over a century. The hybrids are relatively new. The name used for the hybrids is Ipomoea × imperialis.
The ones I’m growing this year are those sold as Mt. Fuji Mix. These appear to be the result of several distinct but similar breeding lines - that is to say, flower color is evidently not the only feature which distinguishes the plants. In the group planted here this year, there have been (only) two colors: a rich purple blue and a pale, dusty pink. So far the vines are at best four feet long and the sparse foliage, sometimes marked with silver-white splotches and streaks, is not much bigger than that of bindweed (although shaped differently).
I gave these what for me has in the past always been appropriate morning glory treatment: I planted the seed and then forgot them. The less than spectacular results I’m getting tell me that these Japanese hybrid sorts require better treatment. In Japan they are typically pampered as pot plants.
Google morning glory and Japan in English and you should hit some links which will get you started on seeing how they are grown and shown in Japan. If you are adventurous, confine your hits to results in Japanese. The Japanese have cultivated the arts of presentation and staging to high degree. Until the Internet made so much available, this was unknown to most of us: now a bit of time spent with a good search engine will result in glimpses of Japanese morning glory shows, tree peony shows, iris shows, chrysanthemum shows, camellia shows – even goldfish shows. Try it: I’m sure you’ll agree that it was time well spent.