 All trumpet vines, also called trumpet creepers, are tolerant of dry conditions, but they'll grow and bloom more heavily if you keep them moist at all times. What you want to avoid is high nitrogen fertilizers near them. That can result in excessive stem growth and fewer or no flowers. Prune to shape and guide the plant over its support, but avoid heavy shearing. As with too much nitrogen, heavy pruning can lead to strongly vegetative growth.