Coreopsis gigantea aka Giant Coreopsis

Coreopsis gigantea — currently treated as Leptosyne gigantea Kellogg by Kew's Plants of the World Online — is a striking woody member of the daisy family (Asteraceae) endemic to the coastal cliffs, dunes, and chaparral hillsides of central and southern California, northern Baja California, and Guadalupe Island. Commonly known as giant coreopsis or giant tickseed, it is one of the most architecturally distinctive plants of the California coast, growing as a stout, succulent-stemmed subshrub that can reach about 2.5 to 3 meters (8 to 10 feet) tall. The thick trunk — 4 to 10 centimeters in diameter and up to a meter tall — branches into a rounded crown, giving older specimens the silhouette of a miniature tree.

The plant follows an unusual seasonal rhythm, the opposite of most temperate species. During California's wet winter and spring, it flushes with bright green, finely divided, fennel-like leaves up to 30 centimeters long, then erupts into masses of yellow, daisy-like flower heads 6 to 20 centimeters across. Flowering peaks from late winter through spring and into early summer. As the long dry summer arrives, giant coreopsis drops its foliage and goes summer-dormant, leaving the bare, pale, sculptural branches that have made it a favorite subject for photographers along the Channel Islands and adjacent mainland bluffs.

In cultivation it asks for the conditions of its native habitat: full sun, sharp drainage, lean sandy or loamy soil, and a near-frost-free climate. It tolerates a range of soil pH from mildly acidic to mildly alkaline and is reliably drought-tolerant once established, with Plants For A Future rating it hardy in USDA zones 10–11 and UK zone 8. Cold tolerance bottoms out at roughly −4 °C (25 °F), and waterlogged winter soils are the main cause of failure outside its natural range; in cooler climates it is best grown under glass. Propagation is straightforward from seed sown in early spring, by division, or from basal cuttings taken in late spring.

Giant coreopsis is most often used as an ornamental in native plant, drought-tolerant, wildlife, and coastal-restoration gardens. Its flowers are visited by a wide range of native bees and other insect pollinators, and Plants For A Future records that the flowers and stems yield an orange to red-orange dye. It has no documented edible or medicinal uses, and the genus Coreopsis is listed as non-toxic to dogs, cats, and horses by the ASPCA. Conservation-wise, NatureServe has assigned it a global rank of G3G4 (vulnerable to apparently secure), reflecting its restricted coastal range and the pressures of habitat loss, though it is not currently on the IUCN Red List.