Salvia guaranitica ‘Black and Blue’ is a popular, vibrant plant known for its striking deep cobalt-blue flowers emerging from nearly black calyxes. This cultivar is often grown as a perennial in warmer zones (USDA zones 7-10) but is treated as an annual in colder regions due to its tenderness. Regular pruning is a beneficial practice for this plant, as it promotes vigorous new growth, maximizes the production of its blooms, and helps maintain a dense, tidy garden appearance.
Timing the Pruning Schedule
The best time to prune depends heavily on the type of pruning needed and the local climate where the plant is growing. Gardeners need to differentiate between the light, ongoing maintenance and the single, major annual reduction. Maintenance pruning should be performed frequently throughout the active growing season, which generally runs from late spring through fall.
The major annual cutback has two primary windows, with the choice depending on the potential for hard frost. In areas with cold winters, the largest cutback is often delayed until early spring, just as new growth begins to emerge from the base. This timing allows the old, hollow stems to provide a small amount of insulation and protection for the crown of the plant during the winter months. Warmer climates without a significant frost danger can perform the hard cutback in late fall or early winter after the plant has finished its main bloom cycle.
Routine Maintenance Pruning
Routine pruning is performed throughout the summer to encourage a continuous flush of new flowers and to shape the plant. The primary action is deadheading, which involves removing the spent flower spikes before they can set seed. Removing these faded blooms redirects the plant’s energy from seed production back into creating new flower buds. Deadheading should be done by making a clean cut just above a set of healthy leaves or a small side shoot that is already forming a new flower spike. This method keeps the plant looking fresh and encourages the next wave of blooms.
Gardeners can also pinch back the tips of non-flowering stems earlier in the season to promote lateral branching. This results in a denser, less “leggy” plant structure. When pinching, remove only the top few inches of a stem, cutting just above a leaf node where new shoots will form.
The Annual Hard Cutback
The annual hard cutback is the most significant pruning event, designed to rejuvenate the plant and prevent it from becoming overly woody or sparse. This reduction is necessary because Salvia guaranitica produces new, vigorous flowering stems from the base each year. The goal is to remove most of the previous season’s growth, stimulating a strong, full plant the following season. When performing the hard cutback, you should reduce the overall size of the plant by approximately one-half to two-thirds. In perennial zones, the stems can be cut back to a woody framework of about 6 to 12 inches above the ground, or even lower to just above the first signs of new growth near the crown.
Always use sharp, clean shears or loppers to make cuts. This ensures a smooth surface that heals quickly and reduces the risk of disease entry.
As noted, the debate between fall and spring pruning is often settled by climate. Leaving the old stems in place through winter offers a measure of cold protection to the crown in colder regions, making a spring cutback the preferred method. However, in mild climates, a fall cutback provides an immediate, tidy appearance for the garden. Regardless of the timing, this deep cut is beneficial for the plant’s structure and flowering capacity.
Managing Spread and Runners
Salvia guaranitica has a tendency to spread through underground stems known as rhizomes, or runners. These runners extend outward from the main clump and produce new plants, which can allow the salvia to colonize an area quickly, particularly in warm, favorable conditions. This spreading habit may cause the plant to intrude on neighboring plants or garden paths. To manage this spread, gardeners should physically remove the unwanted new shoots as they appear away from the main plant. These new shoots, which are easily identified as small stems emerging from the ground, can be dug up and separated from the main root system.
Digging up and dividing the plant’s main clump every few years in early spring or fall can also help control its size and provide new, more vigorous plants for other areas of the garden.