I apologize for this delayed reply to your gardening question and hope it is still helpful to you.
Plumbago is a fairly tough drought tolerant plant once established. However in a container and for a while after planting while it is trying to get roots established it is going to need regular moisture or it will brownout and die. I suggest you continue to water them as long as there is some green on the plants and they may well recover and be fine. I generally plant Plumbago about 5 feet apart but they can be planted closer or farther than that if you wish.
Thanks for the question. Best wishes for a wonderful gardening season. Please stop in again soon!
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