Hi Mel:
I've never used, nor have I ever recommended, "root hormone" powder for use in new tree plantings projects. I firmly believe your newly planted trees will survive just fine without the root hormone.
Simply keep these newly transplanted conifers adequately watered throughout this drought and oppressive heat wave. Consider applying a little bit of fertilizer (N-P-K) beginning the spring of 2015 as I'm a firm believer in delaying fertilization of newly planted trees.