The genus Salvia, commonly known as sage, is a large and diverse group of plants belonging to the mint family, Lamiaceae. With over 900 species, Salvia includes annuals, herbaceous perennials, and woody subshrubs. Gardeners propagate sages to expand displays, control plant size, or rejuvenate older specimens. The method of propagation depends entirely on the specific root structure of the species.
Identifying Salvias Suitable for Division
Division is only appropriate for certain types of sage plants. This technique relies on the plant having a fibrous, clumping root system that can be cleanly separated into smaller, viable sections. Herbaceous perennial Salvias, such as Salvia nemorosa or Salvia x sylvestris, typically form the dense root crowns necessary for successful division. These clumping varieties are ideal candidates for propagation every two to four years.
Root structure is the determining factor, as plants with woody stems or taproots do not respond well to division. Woody shrub Salvias like Salvia microphylla or the culinary herb Salvia officinalis should not be propagated this way. Attempting to cut the central root of these varieties, which is often a single, deep taproot, causes too much damage for the plant to recover. For these sages, propagation through stem cuttings is a more reliable method.
Optimal Timing and Preparation
Timing the division correctly is important for ensuring the survival of the new divisions. The best time to divide these perennials is when the plant is dormant: either in early spring as new growth emerges, or in early fall after the plant has finished flowering. Dividing in the spring allows new sections to establish roots before summer heat arrives. Dividing in the fall must be done early enough for plants to develop a root system before the ground freezes solid.
Proper preparation minimizes transplant shock and boosts the chances of survival for both the parent plant and the new divisions. Water the Salvia deeply the day before division, especially if the soil is dry. This hydrates the roots and makes the soil easier to work with, helping keep the root ball intact during lifting. Cutting back the foliage to about six inches before digging reduces moisture the leaves will transpire, placing less demand on the newly disturbed root system.
The Physical Process of Dividing Salvia
To begin, carefully loosen the soil around the entire plant for removal. Use a spade or garden fork to dig a circle around the Salvia clump, extending slightly beyond the plant’s spread and angling the tool inward to avoid cutting roots. Once the plant is lifted, gently shake off loose soil to expose the root ball and identify natural separation points.
The root ball of a clumping Salvia can often be pulled apart by hand into two or three smaller sections, especially if the plant is not overly dense. For tightly bound or older root masses, use a sharp knife, a hori hori knife, or the edge of a clean spade to make vertical cuts through the crown. Each resulting division must contain several healthy shoots and a sufficient portion of the fibrous root system to support new growth.
The divisions should be replanted immediately at the same soil depth as the original plant to prevent the crown from drying out or rotting. Dig the new holes roughly twice the width of the root ball to give the roots space to spread into the surrounding soil. After backfilling, thoroughly water the new divisions to settle the soil and eliminate air pockets. Keeping the soil consistently moist and providing temporary shade helps the new Salvia plants establish themselves.