Propagating Star Anise Trees Using Layering and Grafting Methods
Propagating star anise through layering and grafting is fast and effective compared to traditional methods
However, propagating star anise trees from seed often results in high variation rates, uneven growth, and late harvest times. Therefore, grafting is considered an effective solution to preserve the superior characteristics of the mother plant, shorten the basic construction period, and improve the yield and quality of star anise orchards.
Advantages of the Grafting Method
Propagation by grafting combines a rootstock (a seedling grown from seed) and a scion (taken from an elite mother plant). This method offers many outstanding benefits. First, grafted trees retain the genetic characteristics of the mother tree, such as high yield, large fruit, high essential oil content, and good resistance to pests and diseases. Second, grafted trees grow faster and shorten the time to harvest, typically yielding after only 4–5 years of planting, whereas seed-grown trees can take 7–8 years. In addition, grafted trees show high uniformity, which facilitates care and harvesting.
Selecting Rootstocks
Rootstocks play an important role in determining the vigor and adaptability of star anise trees. Rootstocks are typically nursed from the seeds of healthy, vigorous, disease-free star anise trees. Seeds are harvested from ripe fruits, cleaned, and then sown into loose, nutrient-rich potting soil. After about 8–12 months, when seedlings reach a height of 25–40 cm with a stem diameter of about 0.5–0.8 cm, they can be used as rootstocks. The plants must grow evenly, have straight stems, be free of deformities, and show no signs of disease. Prior to grafting, they need good care to ensure vigorous health and high graft union success rates.
Selecting Scions
Scions are collected from certified mother trees that demonstrate consistently high yield and excellent quality. Semi-mature branches (neither too tender nor too woody) should be chosen, with a diameter equivalent to or slightly smaller than that of the rootstock. The branch must be healthy, pest-free, and bear distinct dormant buds. The best time to harvest scions is in the early morning or cool late afternoon when plant moisture levels are high. After cutting, keep the scions in cool conditions to prevent dehydration. A damp cloth or plastic bag can be used to temporarily maintain moisture before grafting.
Grafting Seasons
Star anise tree grafting is usually carried out during two main seasons: spring (February–April) and autumn (August–October). During these periods, the weather is cool and humidity is high, which favors healing and scion shoot development. Avoid grafting during periods of intense heat or prolonged severe cold, as these conditions reduce the survival rate.
Common Grafting Methods
Various grafting methods are applied to star anise trees, among which bud grafting and scion grafting are the most popular. Bud grafting (T-budding): Make a T-shaped incision on the rootstock and gently peel back the bark. Next, remove a bud from the scion branch, insert it into the incision, and wrap it securely with plastic tape. This method conserves plant material and yields a high survival rate when performed properly. Branch grafting (side-cleft grafting or approach grafting): Cut off the top of the rootstock, make a small cleft, bevel the scion wood, and insert it into the cleft. Secure the union firmly with tape and cover it completely. This method is well-suited for rapidly multiplying large numbers of seedlings.
Grafting Techniques
When grafting, use a sharp, clean grafting knife to ensure smooth, clean cuts without crushing the tissue. Operations must be quick and precise to prevent moisture loss and limit infection. Once completed, seal the graft union thoroughly with specialized plastic tape to preserve moisture and stabilize the joint. After about 15–25 days, if the bud remains green and hydrated, it is a sign of a successful graft. As the new shoot develops, remove the tape at the right time to avoid constricting plant growth.
Post-Graft Care
Post-graft care is a decisive factor in the survival rate and seedling quality. Grafted plants should be kept under gentle light, shielded from direct sunlight. Regularly water to maintain moisture without causing waterlogging. At the same time, inspect and remove any shoots sprouting from the rootstock to focus nutrients on the graft shoot. After 2–3 months, once the grafted shoot has stabilized in growth, light fertilization can be applied to stimulate development. When the plants reach a height of about 40–60 cm, they are ready to be transplanted to the field.
To improve the efficiency of propagation by grafting, keep the following key points in mind: select authentic, elite mother trees; ensure grafting tools are sanitized; adhere to the appropriate seasonal schedule; care well for rootstocks before and after grafting; and regularly monitor the plants to address any issues promptly.
Propagating star anise trees through grafting is an effective, viable path for developing high-quality star anise raw material areas. Applying the correct techniques not only helps improve yield and product quality but also contributes to conserving and promoting the valuable genetic resources of Vietnamese star anise. Amid rising market demand, replicating this model will bring substantial economic benefits to farmers and the agricultural sector./.