Eucalyptus is a diverse genus of flowering trees and shrubs known for its rapid growth and aromatic foliage. These plants can be started using two primary horticultural methods: sexual propagation through seed or asexual propagation using vegetative cuttings. Both approaches require specific environmental conditions and preparation steps for successful establishment.
Starting Eucalyptus from Seed
Propagating eucalyptus from seed requires breaking the plant’s natural dormancy mechanism before sowing, often achieved through stratification or scarification. Many varieties benefit from cold stratification, where seeds are kept moist in a refrigerator (35–40°F) for four to six weeks. This process mimics the natural chilling cycle, signaling that conditions are right for germination.
For species with a hard seed coat, scarification is necessary to allow water to penetrate the seed embryo. This is accomplished by pouring near-boiling water over the seeds and allowing them to soak and cool naturally for 12 to 24 hours. After pre-treatment, seeds should be sown in a sterile, fine-textured seed-starting mix that offers excellent drainage and aeration.
Sowing should be done shallowly, with seeds lightly covered with the growing medium or coarse sand, as many eucalyptus seeds require light to trigger germination. Containers must be kept consistently moist but not waterlogged, and placed in a bright, warm location. Once seedlings emerge and develop their first true leaves, they can be carefully transplanted into individual pots.
Propagating Eucalyptus from Cuttings
While seed propagation is reliable, using cuttings is the only way to ensure the new plant is genetically identical to the parent, though this method is often more challenging. The most successful cuttings are taken in late spring or early summer from semi-hardwood growth—new stem tissue that has begun to mature but is not yet fully woody. Choosing the right material helps overcome the species’ natural resistance to rooting.
Cuttings should be four to six inches long, taken with a clean blade just below a leaf node. Leaves on the lower half of the stem must be removed to prevent moisture loss and rotting when inserted into the rooting medium. Retaining a few leaves at the top is important, as they drive the photosynthesis necessary to sustain the cutting while roots develop.
To increase the probability of root formation, the base of the cutting should be dipped into a high-strength rooting hormone before planting. Preparations containing Indole-3-butyric acid (IBA) at concentrations between 3,000 and 8,000 ppm are recommended for difficult-to-root species. The treated cutting is then inserted into a well-draining rooting medium, such as perlite and peat moss, ensuring the hormone remains intact.
Creating the Ideal Growth Environment
The initial growth environment must be carefully controlled to support the establishment of both young seedlings and new cuttings. They thrive in consistently warm conditions, with temperatures ideally maintained between 65 and 75 degrees Fahrenheit. Placing the containers on a heated propagation mat helps regulate the temperature of the rooting zone, stimulating both root growth and seed germination.
Light is required, but it must be provided without causing delicate tissues to dry out or scorch. Bright, indirect light is preferable to harsh, direct sunlight during early growth stages. A slightly acidic to neutral soil pH, ranging from 6.0 to 7.0, supports nutrient uptake and is suitable for most eucalyptus species.
Maintaining high humidity (70–90 percent) is important for cuttings that lack a root system to draw moisture. This atmosphere reduces water stress and can be achieved using a clear plastic dome or an intermittent misting system. The rooting medium must remain moist, but the environment requires air circulation to prevent fungal diseases.
Hardening Off and Transplanting Young Plants
Once young eucalyptus plants have developed a robust network of roots, they must be gradually transitioned to outdoor conditions through hardening off. This procedure acclimates the plants to variable temperatures, wind, and intense sunlight, thereby preventing severe transplant shock. The process typically takes 7 to 14 days and involves moving the plants outside for progressively longer periods each day.
Initially, plants should be placed in a shaded, protected location, and only briefly exposed to the elements. Over the course of the hardening off period, they are gradually exposed to more direct sunlight and wind until they can remain outdoors overnight. This slow introduction builds resilience and toughens the plant’s cell structure.
Final transplanting into the garden should occur after all danger of frost has passed, ideally during a mild period when the plants are not under immediate heat or drought stress. The chosen site should provide full sun exposure, as eucalyptus requires substantial light to flourish. After planting, a thorough initial watering is necessary to settle the soil around the roots, and consistent moisture should be maintained until the plant is visibly establishing itself in its new location.