Common peony

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).

An upright, clump-forming perennial of the mint family native to the upper Midwest, Great Plains, and into central Canada, named for its anise-scented foliage. From June through September it carries dense terminal spikes of lavender-to-purple two-lipped flowers above square stems and opposite, toothed leaves. The Lady Bird Johnson Wildflower Center flags it as a nectar source with special value to native bees, bumble bees, and honey bees, and it also draws butterflies and hummingbirds.

Anise-scented sage is a tall, upright perennial in the mint family (Lamiaceae), native to Brazil, Paraguay, Uruguay, and Argentina. NC State Extension and Missouri Botanical Garden PlantFinder describe a bushy, square-stemmed plant 2 to 5 feet tall and wide that carries spikes of deep blue, two-lipped flowers with purple-blue calyxes from July into fall; NC State calls it a reliable nectar source for hummingbirds and butterflies, and notes that carpenter bees rob its nectar by biting a hole in the floral tube. The 'anise-scented' name is only partly earned: Wikipedia describes 'an anise scent when crushed,' but Missouri Botanical Garden PlantFinder says the bruised foliage has a very mild aroma with 'very little if any anise scent.' It spreads by tuberous roots that let it reproduce vegetatively (NC State Extension), so it fills a space rather than staying in a tidy clump. It is winter hardy only to about USDA zone 8a: farther north, grow it as an annual or overwinter cuttings indoors, though NC State notes the 'Black and Blue' cultivar is hardier and will survive milder zone 7 winters if well mulched. Neither NC State nor Missouri Botanical Garden documents an edible use or a toxicity hazard. NC State records, as ethnobotanical history, that the Guarani people of Brazil used it as a sedative; that is not a recommendation to take it, so treat it as a non-food ornamental. It has also naturalized outside South America (Wikipedia records it in New Zealand and Chile), so where winters are mild enough for it to persist outdoors, check your local weed or invasive-plant list before planting it.

Arkansas blue star (Amsonia hubrichtii), also called threadleaf bluestar or Hubricht's bluestar, is a clump-forming native perennial from a tiny wild range in the Ouachita Mountains of Arkansas and Oklahoma that has become one of the most dependable foliage perennials in temperate gardens. It builds a soft, rounded, knee-to-waist-high mound of upright stems clothed in very fine, needle-like, thread-thin leaves, so the whole plant reads as a feathery green cloud through summer. In late spring the stem tips carry loose clusters of small, pale powder-blue, five-pointed star flowers, a quiet but pretty show that draws butterflies and other pollinators. Its headline act comes in autumn, when the fine foliage turns a clear golden-amber that lights up the border and earned it the Perennial Plant Association Plant of the Year for 2011. It wants full sun to part shade and is famously tough, adaptable, and deer-resistant, though it will flop open in too much shade or overly rich soil, so give it sun and a light shearing after bloom if you want it to stay upright.

A clump-forming herbaceous perennial grown for its showy late-season flower heads: masses of tiny star-like flowers borne in flattened cymes 3 to 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 24 inches. 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.

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.