I often wonder why more people don't order plants in what is the most ideal time. Most perennial plants (including trees, shrubs, grasses, and vines) actually establish much better if planted in the fall or winter vs planting in the spring or summer.
Plants placed in autumn have the mild autumn days to begin to grow roots, which will continue at a slower pace over the winter. If you compare an October planted perennial and a same age potted plant that wasn't planted in the ground until May, you will often find that the root mass of the autumn planted plant will be more than twice as extensive as the spring planted plant by midsummer. This results in more foliage growth and likely more flowers in the first season, as well as a headstart for getting through the first hot (and possibly dry) summer.
It just makes sense! Please consider autumn or winter orders (where the ground doesn't freeze) for even more success!