advice for a white, low-maintenance mother's day garden

I am planning a four tier garden for my mother who loves white flowers who will likely kill anything she has to water. Also limiting this to perennials or reseeding annual. Oddly enough, I love color and have always more or less ignored white flowers! I have plenty of colorful flower and vegetable seeds to trade. Advice without seed is also very welcome! Mrslauramay (at) yahoo.com