Salvia patens aka Blue Sage

Salvia patens is a perennial known as gentian sage. Other names include blue-flowered sage and spreading blue sage. It belongs to the mint family, Lamiaceae. Its native range runs from Mexico to Guatemala. Kew places it in the seasonally dry tropical biome. The plant grows from tubers beneath the soil. It forms a clump and loses its leaves seasonally.

Garden plants reach about 1.6–3.3 feet [0.5–1 metre] in height. Their spread falls within the same range. They take two to five years to reach full size. The leaves range from egg-shaped to triangular. They can reach about 0.66 feet [0.2 metres] long. Blue flowers have two lips and reach 0.16 feet [0.05 metres] long. They form a large, open panicle above the foliage. These loose flower clusters give the plant its main garden interest.

Choose a sheltered site with plenty of sun. The plant also tolerates some light shade. The RHS recommends light soil with humus and moderate fertility. Keep the soil moist, but let excess water drain. Suitable soils include chalk, loam and sand. Acid, neutral and alkaline conditions all suit it. The RHS gives it a UK hardiness rating of H3. This limits outdoor winter survival to coastal and relatively mild areas. Chicago Botanic Garden lists USDA zones 8–10. In colder places, the RHS describes overwintering tubers in damp potting compost.

Gentian sage suits beds, borders and informal cottage gardens. It can also grow in pots on patios. The RHS includes coastal, courtyard and wildlife gardens among its uses. It also lists greenhouse and conservatory growing. Cut off spent flower spikes to extend the flower display. Raise new plants from seed sown in pots. Basal cuttings and softwood cuttings offer other ways to propagate it. Take these in spring or early summer.

The RHS reports few routine pest problems for this species. Disease can still affect its roots and foliage. Listed risks include powdery mildew, verticillium wilt and root rot. Foot rot can occur, while honey fungus is rare. Good drainage remains part of its stated growing needs. The supplied sources give no fruit description or food use. They also provide no species-level finding on toxicity.