Acid can be used in both early and late stages of layering, but its purpose and application differ significantly. In early stages, it aids in root formation, while in later stages, it can help with nutrient availability.
In the *early* stages of layering, specifically when preparing the stem for root development, a mild acid can be beneficial. This is because acids, such as diluted vinegar or lemon juice, can help to slightly weaken the outer layer of the stem, encouraging the plant to produce root hormones (auxins) at the point of contact with the soil or rooting medium. This promotes faster and more reliable root formation. The acid essentially acts as a mild irritant, stimulating the plant's natural defense mechanisms, which include root development.In the *later* stages, after roots have begun to form, the role of acid shifts. At this point, the focus is on providing the developing roots with the nutrients they need to thrive. Some plants, particularly those that prefer acidic soil (like blueberries or azaleas), benefit from a slightly acidic growing medium. Introducing a mild acid at this stage can help to lower the pH of the soil, making nutrients like iron, manganese, and phosphorus more readily available to the roots. This can lead to healthier and more vigorous growth of the newly layered plant. However, it's crucial to monitor the pH level carefully to avoid over-acidifying the soil, which can be detrimental.
Always dilute acids significantly before applying them to plants. A concentration that is too strong can damage or even kill the plant tissue. Start with a very weak solution and gradually increase the concentration if needed, while carefully observing the plant's response.