I know they like their feet in the shade and tops in the sun. If you have great foliage and no buds or flowers, they have plenty of nitrogen. Look for a fertilizer that is 5-10-10 or something similar. That will give them more phosphorous and potassium than nitrogen. Avoid fertilizing in summer and fall. And, give them a good soaking from time to time, especially going into winter.
Thanks for writing!