I want to plant New Dawn Roses and Jackmanii clematis together along a fence. Would planting the roses now in the spring and then the clematis in the fall be a good way to start?
Planting them both now is ideal as they will both need the same care this year. However, I couldn't begin to tell you how to properly fertilize the combination.
Planting them together should be fine. I planted New Dawn (or Dr. Van Fleet, I think I ended up with) on one side to grow over the arch, and then a Perle D'Azur on either side. My clem that's on the side with the rose is planted approx 14" from ND, which is too close, but they seem to be doing alright so far (this year will be their 5th together). I fertilize everything with the same stuff - alfalfa, compost, seaweed, manure, anything organic that I can get my hands on. Have fun!