Hi Charles,
I think our summers are hot enough, I think getting full sun is key the more sun the better.
I thought mine grew pretty well considering one was severally root pruned, another was sick that returned to health and another I took cuttings from all summer.
I had mine growing in water with the roots 1/2 submerged all summer I think that the water helped retain a little heat for the roots to grow better at night.
This spring am going to feed them a lot more to get that early growth going (trying to get a snowball effect of growth going sooner).
I'll also be putting them in water sooner (basically a week or two after I see some green needles emerge).