transplanting a 6 foot jasmine in portland oregon
You can safely transplant jasmines from fall through spring--basically anytime that the ground is not frozen. However, because transplanting jasmines usually involves doing substantial pruning, and pruning jasmine should be done in spring just before new growth starts, or right after bloom.
There are many different species of jasmine that are grown here--the Sunset Western Garden Book lists at least 9, not counting Star Jasmine (Tracheopermum jasminoides), which is actually in an unrelated family. While most people think of most jasmines as vines, they lack twinging tendrils, and have to be tied to their supports, or they revert to their natural growth habit, Which is basically a mound, or green haystack. Transplanting that haystack is probably going to involve cutting out a lot of dead twigs and misplaced branches. All that cutting is going to prompt a surge of new growth, and that tender new growth will be damaged by winter weather. Which is why it is pruning jasmines should be done in spring. (An excellent resource for pruning jasmines is The American Horticulture Society Pruning & Training, by Brickell and Joyce. The authors are obviously fond of this family of plants, and provide detailed information. The book is readily available from local libraries.)