Symphyotrichum oolentangiense

This well-behaved aster does not usually spread, unlike some aster species. Numerous blue-lilac flowers emerge in September and are beloved by butterflies. Adaptable to most soils as long as they're well-drained. Heavily mulched beds will prevent this short-lived perennial from reseeding, shortening its life in the garden.

Photo by Joshua Mayer and Henrique P.