Trimming cannabis on the stem refers to the process of removing leaves and other unwanted plant material while the plant is still attached to its main stem. This method of trimming has several advantages, including:

1. Better handling: Trimming on the stem allows you to grip the plant by the stem while you trim. This reduces the amount of direct contact with the buds, preventing trichomes (the resin glands containing cannabinoids and terpenes) from being damaged or rubbed off.
2. Improved drying process: By leaving the buds on the stem, you can hang the plant upside down to dry, which helps ensure proper airflow and even drying. This method can prevent mold and mildew and often leads to better preservation of terpenes and cannabinoids, ultimately improving the quality of the final product.
3. Easier to manage: Trimming on the stem can make the overall process more organized and manageable, as the plant remains intact during the trimming process. This can be particularly helpful when dealing with a large number of plants.
4. More control over trimming: Trimming on the stem allows you to have better control over the process, making it easier to remove unwanted material and shape the buds to your preference.
5. Slower oxidation: Leaving the buds on the stem during the initial drying phase can slow down the oxidation process, helping to preserve terpenes and cannabinoids, which can contribute to better flavor, aroma, and potency in the final product.
6. Ergonomics: Some growers find it more comfortable to trim cannabis on the stem, as it allows for a more natural hand position and reduces the risk of hand strain during the trimming process.

However, it’s essential to note that the choice of trimming method ultimately depends on personal preference, available resources, and the size of the harvest. Some growers may prefer to trim cannabis off the stem (also known as wet trimming or bucking) because it can be more efficient and may help speed up the drying process.