Propagating thyme allows you to multiply your stock without relying on seeds, which often produce variable results or take a long time to mature. Thyme is a popular choice for this method because it is highly reliable and provides an economical way to expand an herb garden or replace older, less productive plants. Starting new thyme plants from a piece of an existing one ensures the new plant is a genetic clone, guaranteeing the same flavor and growth habit as the original.
Propagating Thyme by Cuttings
The most dependable method for generating new thyme plants involves taking stem cuttings, ideally performed during the active growth period in late spring or early summer. Select healthy, flexible stem tips that are neither woody nor actively flowering. Using clean, sharp shears, cut a three- to four-inch section just below a leaf node, which is the point on the stem where hormones concentrate to initiate new growth.
After taking the cutting, carefully strip the foliage from the bottom two inches of the stem to expose the nodes where roots will emerge. This prevents submerged leaves from rotting, which can introduce fungal disease. Dipping the cut end in a powdered or gel rooting hormone can significantly increase the speed and success rate of root development. The hormone stimulates cell division at the cut site.
The prepared cutting can be rooted in a few different mediums, with a sterile, well-draining mix being the most common choice. A blend of half sand or perlite and half potting soil provides the necessary aeration to prevent rot while retaining moisture. Create a small hole in the medium with a pencil before inserting the cutting to avoid rubbing off any applied rooting hormone. Alternatively, the cutting can be placed in a glass of water, ensuring only the leafless portion is submerged, and the water is changed every few days.
Increasing Your Stock Through Division
Division is a faster propagation method that provides an instant new plant, but it requires an existing, mature plant that has been growing for at least two to three years. This process is best undertaken in early spring before intense new growth begins, or in early fall after the summer heat subsides. Division is beneficial for rejuvenating thyme plants that have become leggy, woody, and less aromatic over time.
Begin by carefully digging up the entire thyme clump, working a trowel or spade in a wide circle around the perimeter to preserve the shallow root system. Once lifted, the rootball can be gently pulled apart by hand or, if densely matted, sliced with a clean, sharp knife into smaller sections. Each separated section must possess sufficient healthy roots and green top growth to ensure its survival.
The newly created divisions should be immediately replanted into their new locations at the same depth they were previously growing. Trimming back the top foliage by about one-third reduces the amount of water the leaves demand, allowing the plant to focus energy on growing new roots. This technique minimizes transplant shock, and a thorough watering immediately after replanting helps settle the soil around the roots.
Essential Care for Newly Propagated Thyme
Once cuttings have developed roots (typically after four to eight weeks) or divisions have been settled, the focus shifts to providing the specific environmental conditions thyme needs to thrive. Thyme is a Mediterranean herb, requiring a location that receives a minimum of six to eight hours of direct sunlight each day. Insufficient light results in weak, spindly growth and a diminished concentration of the aromatic oils that give the herb its flavor.
The most frequent cause of failure in newly propagated thyme is overwatering, which leads to root rot. The soil must be allowed to dry out slightly between waterings, mimicking its native arid conditions. When watering, apply enough to thoroughly moisten the soil, then allow excess water to drain completely. Well-draining soil, such as a mix incorporating sand or grit, is necessary to prevent standing water near the delicate new roots.
For plants rooted indoors or in a protected environment, “hardening off” is necessary before moving them permanently outdoors. This involves gradually acclimating the young plants to outdoor conditions, including direct sunlight, wind, and temperature fluctuations, over a period of one to two weeks. Start by placing them in a sheltered, shady spot for a few hours each day, progressively increasing the duration and exposure to sun. This prepares the thyme for its permanent outdoor home and ensures long-term success.