Salvia guaranitica ‘Black and Blue’, or Black and Blue Salvia, is a vibrant garden plant. It displays deep cobalt blue tubular flowers emerging from contrasting black calyces, creating a dramatic visual effect. Its abundant blooms appear from late spring through fall, attracting hummingbirds, bees, and butterflies. Native to Brazil, Paraguay, and northern Argentina, it grows as a tender perennial or subshrub in warmer climates and as an annual in cooler regions.
Planting and Site Selection
Black and Blue Salvia thrives in full sun, tolerating partial shade in hotter climates. It benefits from some shelter from strong winds. This plant typically reaches 3 to 5 feet tall and 2 to 5 feet wide. Space plants 2 to 3 feet apart to ensure proper air circulation and full development.
Black and Blue Salvia prefers well-draining soil rich in organic matter. It thrives in slightly acidic to neutral soil. If your garden has heavy or poor soil, amend it with a 3-inch layer of compost. This significantly improves drainage and nutrient content.
Plant potted salvias after the last spring frost. Dig a hole twice as wide as the root ball, but no deeper than its current depth. Place the plant in the hole, ensuring the top of the root ball is level with the surrounding soil. Backfill with soil, firming it gently to remove air pockets, then water thoroughly to settle the soil. Apply a 2- to 3-inch layer of mulch around the base to retain moisture and suppress weeds.
Ongoing Maintenance
Water Black and Blue Salvia consistently, especially during establishment and dry periods. Newly planted salvias need deep watering two to three times per week until roots are established. Mature plants require moderate watering, about once per week, allowing the soil to dry slightly between waterings. While drought tolerant, established plants benefit from occasional deep watering during prolonged dry spells to support vibrant blooms. Water at the soil level to reduce the risk of fungal issues.
Black and Blue Salvia does not require heavy fertilization, but occasional feeding enhances growth and flowering. Apply a balanced slow-release fertilizer in early spring. During peak blooming, a phosphorus-rich fertilizer every four to six weeks encourages more abundant flowers. Container-grown plants often benefit more from regular fertilization than those in the ground. Over-fertilization, especially with excessive nitrogen, can promote foliage at the expense of flowers.
Regular pruning and deadheading maintain the plant’s shape and promote continuous flowering. Removing spent blooms encourages more flowers throughout the growing season. If the plant becomes leggy or overgrown, a light midseason pruning, trimming back about one-third of the growth, helps maintain a bushier form.
Black and Blue Salvia can be susceptible to certain pests and diseases. Common fungal issues include powdery mildew and root rot, often caused by poor air circulation or overly wet soil. Ensure good air circulation and well-draining soil to prevent these problems. Pests like spider mites, aphids, whiteflies, and leafhoppers may appear. For minor infestations, a strong jet of water dislodges pests; for persistent issues, use insecticidal soaps or neem oil, with caution around pollinators.
Winterizing and Perennial Care
Black and Blue Salvia is a tender perennial or subshrub, hardy in USDA Zones 7 to 10. In regions with colder winters (below Zone 7), it is typically grown as an annual.
In perennial zones, prepare Black and Blue Salvia for winter to ensure its return. After the first frost causes foliage to die back, cut stems down to 3 to 6 inches above the soil line. In borderline zones, apply a 4 to 6-inch layer of mulch around the base for root protection against freezing temperatures.
In colder climates, manage Black and Blue Salvia through winter in two ways. Treat it as an annual, allowing it to die back after frost and replanting new specimens the following spring. Alternatively, overwinter the plant indoors by digging it up before the first hard frost, potting it, and moving it to a cool, bright, frost-free location like a garage or basement. During indoor overwintering, reduce watering to about once a month, ensuring the soil does not become waterlogged. The root ball can also be divided into smaller sections before potting to manage size.