Coneflower/Echinacea is an old favorite and can be completely neglected, they will grow anywhere in full sun. Even in poor soil. They also spread nicely. Looks nicely when paired with Russian sage - blue and pink
Power Perennials: Plants That Thrive No Matter What
(Ordered two, Spring Black Knight Butterfly Bush. An easy-to-grow shrub that should be an essential feature in all yards. Butterflies and hummingbirds can't resist the honey-scented blooms. Place near a patio or pathway and enjoy their fragrance.
Kent oregano is a perennial herb that is drought tolerant and a favorite of hummingbirds. It has aromatic foliage and blooms pink or lilac flowers late spring-early fall.It prefers full sun-part shade and grows tall. Used in borders, containers, cutti
Commonly called Basket of Gold, perennial alyssum makes a wonderful wall or rock garden plant. Every spring it develops masses of cheerful yellow flowers that look terrific tucked between rocks and boulders. - Flower Beds and Gardens