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Here are the steps:
1. Choose a healthy stem of the plant. Ideally, select a new growth that is flexible and about one year old. Older branches are less likely to root.
2. Girdle the stem by removing a strip of bark 1.8 to 2.5 cm wide. The width of the girdle should generally be three to four times the diameter of the branch. This will concentrate auxins and nutrients at the girdled area, promoting root formation.
3. Cover the girdled area with a black plastic bag to prevent exposure to direct sunlight.
4. It is important to squeeze the sphagnum moss tightly to remove excess moisture. Roots tend to grow when they seek moisture; too much water can reduce rooting rates.
5. Wrap the moistened sphagnum moss around the girdled area, cover it with polyethylene film, and secure it with rubber bands or string. However, be cautious with string as it can cut into the stem. Using tape, like duct tape, is also effective. I personally use duct tape for air layering.
Tips for Increasing Success Rates
Timing and season are crucial. The best time is during the growing season from spring to summer when the plant is actively growing and more likely to root. Using rooting hormone and managing humidity appropriately can also promote rooting. Effective rooting media such as vermiculite or sphagnum moss are recommended. The optimal temperature for air layering is around 25°C to 30°C. Under these conditions, rooting generally completes within 2 to 4 months depending on the species. From my experience, avocados take about 4 months to root. Additionally, targeting drooping branches for layering can be effective as these are often more likely to root.
Advantages of Air-Layered Fruit Tree Seedlings
All avocado varieties have highly heterozygous genes, meaning the egg cells and pollen grains have unknown genetic compositions, making each seedling genetically unique. Therefore, it is impossible to produce genetically uniform planting materials from seeds. Even seeds collected from a single tree for rootstock production will result in seedlings with varying characteristics. When seeds are randomly collected from different trees, this non-uniformity becomes even greater. In some cases, achieving uniformity in rootstock characteristics is crucial for the success of an avocado orchard. For instance, the rootstock's reaction to high lime content and soil and irrigation water salinity, as well as its response to soil-borne diseases like Phytophthora cinnamomi, are important. Currently, in the same orchard, you can find trees that suffer greatly from salinity and others that show little or no damage, which can be attributed to inherent differences among the rootstocks. By producing genetically uniform seedlings, we can reduce disease and improve fruit quality.
Important Considerations
Selecting a healthy plant is crucial. Choose a stem that is free from diseases and pests. Maintaining appropriate humidity is also important. Too low humidity hinders rooting, while too high humidity can cause the stem to rot. Providing suitable light conditions is also essential. Avoid direct sunlight and provide moderate light to ensure smooth rooting. Unflowered trees are more vigorous in their vegetative growth and tend to root more easily. This tree has flowered before but has not borne fruit. After air layering, I plan to graft a desirable variety.
It is important to wait until fine roots have emerged before removing the air layer. The first roots that appear are generally thick, and you should wait for the development of fibrous secondary roots. In avocados, for example, some have many fine roots while others have few, with thick roots being more prominent. Ideally, you should wait for the fibrous roots before removing the layer. Many fruit trees root within 2 to 4 months, so remember the date you performed the air layering and start checking around that time.
If you delay removing the air layer, the branch can suffer from severe drying stress. Air-layered branches dry out quickly, and in dry environments like recent summers in Okinawa, they can dry out and die even if they have rooted. The girdling prevents adequate water transport to the branch, causing it to dry out. Therefore, timing is crucial. This time, I performed air layering in March and planned to remove it in July, but this period might be particularly prone to drying. Trying different timings might yield better results. You should test different periods to find the most efficient timing.
Finally, when transplanting the air-layered seedling into a pot, use a deep pot. Air-layered seedlings often have weak roots, so it is important to promote strong root growth. Deep pots are recommended for this purpose.
Негізгі бет How to propagate avocados by layering.
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