Black and Blue Salvias (Salvia guaranitica) are popular ornamental plants, cherished for their striking blue flowers and contrasting black calyxes. They provide continuous color from mid-summer until the first frost, attracting gardeners and hummingbirds. Ensuring their return, especially in colder climates, depends on proper winter care.
Understanding Black and Blue Salvia Hardiness
Black and Blue Salvias are tender perennials; their winter survival varies by climate. Native to South America, they are accustomed to warmer conditions, making them reliably perennial in USDA Plant Hardiness Zones 8-10.
In warmer zones, salvias often survive winter with minimal intervention, regrowing from their rootstock. In colder zones like USDA Zone 7, they are marginally hardy, requiring winter protection. For zones colder than 7, they are typically grown as annuals or need specific overwintering strategies. Understanding your hardiness zone is the first step for appropriate winter care.
Preparing Black and Blue Salvias for Winter
Prepare Black and Blue Salvias for colder months before the first hard frost. Light fall pruning should focus on tidying or removing spent flower stalks. Leaving some top growth offers insulation to the crown and roots; heavy autumn pruning is not recommended.
Water in-ground plants adequately before the ground freezes to help them endure dry winter conditions. Once temperatures drop, apply a thick layer of organic mulch (e.g., straw, shredded leaves, pine needles) around the base. This insulates roots from extreme cold and prevents freeze-thaw heaving. For container plants, decide whether to bring them indoors or provide extra outdoor protection.
Overwintering Black and Blue Salvias
Overwintering Black and Blue Salvias depends on your climate and whether plants are in the ground or in containers. For in-ground plants in warmer zones (8-10) or marginal zones (7), a thick 4-6 inch mulch layer around the base protects roots from freezing. In colder areas, in-ground overwintering is less certain, even with mulching. Some gardeners also use cloches or frost blankets during extreme cold snaps for added protection.
Bringing potted Black and Blue Salvias indoors is an effective method for survival in colder climates. Before moving them inside, inspect for pests and clean up any yellowing or damaged foliage. Choose a cool, above-freezing location, such as an unheated garage or cool basement. During their indoor stay, reduce watering significantly, allowing the soil to dry out between waterings to prevent root rot. Fertilization should be withheld throughout the winter. It is normal for plants to enter a dormant state and lose some leaves indoors.
As an alternative, taking cuttings in late summer or early fall can ensure new plants for the following spring. Black and Blue Salvias do not reliably produce viable seeds, making cuttings a preferred method for propagation. This approach allows gardeners in very cold zones, where overwintering large plants is challenging, to preserve the genetics of their favorite plants. Cuttings can be rooted in moist soil or water and kept in a bright, warm location indoors until spring.
Spring Revival for Black and Blue Salvias
As spring approaches and the threat of the last frost passes, Black and Blue Salvias require specific care to emerge from dormancy and begin their new growth cycle. For outdoor plants, gradually remove the winter mulch layer once temperatures begin to warm consistently. This prevents moisture from accumulating around the crown, which could lead to rot. Pruning back the dead top growth should be done after the last frost, when new green shoots start to appear from the base of the plant. This practice encourages vigorous new growth and maintains the plant’s shape.
Indoor-overwintered plants need a gradual reintroduction to outdoor conditions, a process known as hardening off. Begin by placing them outside in a sheltered, shaded spot for a few hours each day, gradually increasing their exposure to sunlight and wind over one to two weeks. This helps them acclimate to the harsher outdoor environment. Once the hardening-off period is complete and all danger of frost has passed, these plants can be moved to their permanent outdoor locations. Resume regular watering and begin a light fertilization regimen as the plants actively start growing, supporting their robust development throughout the season. Patience is beneficial, as initial growth may be slow after the winter rest period.