A bold, clump-forming evergreen perennial from South Africa, grown for big rounded umbels of trumpet-shaped blue (or white) flowers held on tall bare stalks above arching, strap-shaped leaves in mid-to-late summer. It is widely sold as "lily of the Nile," but that is a misnomer — the plant is South African (the Cape provinces and KwaZulu-Natal), not from the Nile. Spectacular and easy in warm climates, this evergreen Agapanthus is frost-tender, so in cold-winter areas it is grown in a container and overwintered under cover. The RHS has given several Agapanthus praecox forms its Award of Garden Merit and rates this evergreen species half-hardy (H3 — needs winter protection).

Asiatic hybrids are the easiest lilies to grow and among the first to bloom — rigid, unbranched 3-4 foot stems carry large, mostly upward- and outward-facing flowers 4-6 inches wide in nearly every color but blue, often with dark basal spotting. The flowers are showy and good for cutting but, unlike most other lily groups, usually have little or no fragrance. Every part of the plant is dangerously toxic to cats.

A clump-forming herbaceous perennial grown for its showy late-season flower heads: masses of tiny star-like flowers borne in flattened cymes 3-6 inches across that emerge rosy pink, deepen to rose-red, and fade to coppery-rust as they die. Gray-green, fleshy, succulent-like leaves form upright clumps to about 2 feet. Easily grown in dry-to-medium, well-drained soil in full sun, it is drought tolerant and attracts butterflies, and its foliage and dead inflorescences persist into winter for added interest.

The classic German or common-flag iris — the presumed parent of most modern bearded-iris cultivars, probably native to southern Europe and the Mediterranean and naturalized widely. Each stalk carries up to six large, usually fragrant flowers in spring: three erect lilac standards above three purple falls marked with brown veins, white bases, and the signature yellow "beard." It has no bulb, spreading instead by creeping rhizomes that form large clumps, with sword-shaped basal foliage to about two feet.

A long-lived native perennial of central and eastern US woodland borders and prairie meadows with deep blue pea-shaped flowers in late spring, blue-green leguminous foliage, attractive black seed pods for winter interest, and a nitrogen-fixing root system (Fabaceae). Larval host for 6 documented butterfly species per NC State (orange sulphur, clouded sulphur, frosted elfin, eastern tailed-blue, hoary edge, wild indigo duskywing) — among the highest Lep-host-count perennials in the eastern flora.

An architectural, branching perennial grown for the metallic steel-blue flush it takes on in summer: small, egg-shaped flowerheads, each ringed by a collar of spiny, silvery-blue bracts, are held on rigid, blue-tinted stems above a basal rosette of leathery, heart-shaped leaves. It is a tough, genuinely drought-tolerant plant for hot, dry, sharply drained, even poor sandy or gravelly soil in full sun — it resents rich, wet ground, where it rots and flops — which makes it ideal for gravel gardens and coastal, seaside plantings, and one of the best long-lasting cut and dried flowers. At the height of summer it is a magnet for bees, butterflies, and hoverflies. It is grown purely as an ornamental and is not eaten.