I have been growing and propagating jasmine for years and I must say, they do get straggly if not cared for from time to time. I do not mean to disagree with Bazram, but I prune much harder this time of year on the older plants. I agree on the younger plants. Jasmine Sambac is my favorite variety of Jasmine and The Grand Duke is one of them as you know. They will get really straggly if not kept pruned. They should not be left get bigger than 2-3 ft. or they will not do too well filling out. As young plants I just keep an eye on them and as I see what I call stragglers, I cut them back. If I were you I would give it a good pruning when it is finished growing. The Duke is a slow grower as you know, so if you cut it back too far you may have to wait for new growth a bit longer. I would shape it up and see what happens. Did you know that the Grand Duke of Tuscany, who your plant is named after, had many plants and made tea from his flowers. One of his famous recipes was for his Chocolate Tea. Just thought you may get a kick out of that. You need to grow a lot of Jasmine to make tea I might add. Good luck and keep us posted. I am sorry I did not reply to your post sooner, but I have been a bit under the weather. I am 90 years old and not as quick as I once was.
