Yes, you absolutely can grow new rosemary plants from cuttings. From a botanical perspective, this method of asexual propagation, known as stem cutting, allows you to create a genetic clone of the parent plant. This is highly efficient as it bypasses the longer and more uncertain process of growing from seed, ensuring the new plant possesses all the desired characteristics, such as specific oil composition, flavor profile, and growth habit, of the original.
The success of propagating rosemary from a cutting hinges on the plant's natural ability to generate adventitious roots. These are roots that form from non-root tissues, typically from a node—the critical point on the stem where leaves emerge. Nodes contain a high concentration of undifferentiated cells called meristematic tissue, which can develop into various specialized tissues. When a cutting is taken and placed in the right conditions, these cells are triggered to differentiate and organize into a new root system, sustaining the cutting as an independent plant.
For the highest chance of success, your cutting must be a healthy, vigorous section of the parent plant. The ideal cutting is a softwood or semi-hardwood stem tip, approximately 4-6 inches long, taken from new growth that has begun to mature but is not yet old and woody. Using a sharp, sterilized blade, make a clean cut just below a leaf node. This increases the surface area from which roots can emerge. Immediately after cutting, remove the leaves from the bottom 1.5-2 inches of the stem. This prevents these buried leaves from decaying in the growing medium, which could lead to fungal infections that jeopardize the cutting.
While not strictly necessary, dipping the stripped end of the cutting into a rooting hormone powder can significantly enhance propagation success. Rooting hormones contain synthetic auxins, a class of plant hormones that stimulate root initiation. They also often include fungicides to protect the vulnerable cut end. After application, the cutting is inserted into a well-draining, sterile growing medium. A mix of perlite and peat moss or a specialized seed-starting mix is ideal, as it provides moisture retention while preventing waterlogging that would cause the stem to rot instead of root.
Once potted, the cutting requires a consistently humid environment. This is because the cutting has no root system to take up water, and it loses moisture through its remaining leaves. By placing a clear plastic bag or dome over the pot, you create a miniature greenhouse that reduces transpiration and maintains humidity. The pot should be placed in a warm location with bright, indirect light. Direct sunlight will cook the cutting inside its humid enclosure. The medium must be kept lightly moist, but never soggy. Roots typically begin to form within 2-4 weeks, and you will know the process is complete when you feel slight resistance when gently tugging on the stem, indicating new roots have anchored the plant.
