Rosemary (Salvia rosmarinus) is a fragrant, evergreen herb prized by cooks and gardeners for its pungent aroma and woody structure. Propagating this plant from stem cuttings is a highly effective, cost-efficient method to increase your stock, whether for culinary use or for landscaping. This technique bypasses the often slow and unreliable process of growing rosemary from seed, instead producing genetically identical clones of the parent plant. Successfully rooting a cutting relies on proper selection, preparation, and managing the environment, all of which encourage the stem to develop its own root system.
Selecting and Preparing the Rosemary Cutting
The ideal time to take rosemary cuttings is during the growing season, typically from late spring through early summer, before the plant begins to flower. Choose semi-hardwood stems, which are the current season’s growth that is maturing and feels firm, but is not yet fully woody. Avoid soft, green tips or very old, woody portions. If the stem gently bends and snaps, it is ready for propagation.
The cutting should be four to six inches long, using a clean, sharp tool like pruning shears. Make the final cut just below a leaf node, the point where a leaf attaches, as this area is receptive to forming new roots. Strip the leaves from the lower half to two-thirds of the stem to prevent them from rotting once submerged or buried.
Comparing Rooting Methods: Water vs. Soil
Gardeners can choose between rooting rosemary in water or directly in a soil-based medium. Water propagation involves placing the prepared cuttings in a clear container filled with clean water, ensuring only the bare stem is submerged. Root development typically begins within two to six weeks. To prevent the stem from rotting, the water must be refreshed every few days.
For the soil method, cuttings are inserted into a well-draining, light medium, such as standard potting soil blended with perlite, vermiculite, or coarse sand. Heavy, moisture-retentive soil mixes must be avoided, as rosemary requires excellent drainage. Before planting, the cut end of the stem can be dipped in a rooting hormone powder or gel, which can improve the speed and success rate. Use a pencil or dibber to create a narrow hole before inserting the cutting to prevent the hormone from being scraped off.
Ongoing Maintenance During Root Development
Cuttings require consistent environmental conditions during root development. Place all cuttings in a location that receives bright, indirect sunlight, such as a windowsill not exposed to harsh, midday sun. Temperatures around 70°F are suitable for encouraging root growth.
Cuttings rooted in a soil medium must be kept evenly moist but never saturated or waterlogged. Overwatering quickly leads to stem rot, to which rosemary is particularly susceptible. To maintain high humidity, a clear plastic bag or dome can be placed over the pot, but this covering should be removed periodically to allow for air circulation.
Acclimating and Transplanting Rooted Cuttings
Cuttings rooted in water are ready for transplanting once they have developed several roots about a half-inch long. These roots require careful handling during the move to soil. For soil-rooted cuttings, successful establishment is indicated by new leaf growth or slight resistance when the stem is gently tugged. Rooting typically takes between four and eight weeks in soil.
Once the roots are established, the young plants should be gradually introduced to regular outdoor conditions, known as “hardening off.” This involves placing the plant outside in a sheltered spot for increasingly longer periods over several days. The rooted cutting can then be transplanted into a permanent pot or garden location using a well-draining medium, such as a cactus mix or standard potting soil amended with grit.