Perilla, also known as Shiso or Kkaennip, is an aromatic herb belonging to the mint family, Lamiaceae. This herb is a staple in many East Asian cuisines, used fresh as a garnish, a wrap for grilled meats, or in traditional medicine. Perilla leaves possess a unique, complex flavor profile that can range from spicy and grassy to notes of anise and cinnamon, depending on the variety. Strategic harvesting throughout the growing season is necessary to ensure a continuous supply and maximize the plant’s overall output.
Optimal Timing for Leaf Harvest
The initial harvest should begin once the plant has established a strong root system and reached a height of at least 8 to 12 inches. The general harvesting window extends from late spring, after the danger of frost has passed, through early fall.
The best time of day to harvest is in the cool morning hours, right after the dew has evaporated. Harvesting during this period minimizes wilting and ensures the leaves retain their highest moisture and oil content, contributing directly to flavor and shelf life. It is important to monitor the plant for any signs of bolting.
Bolting, the development of a central flower stalk, typically occurs as day length shortens in late summer or early fall. Once the plant begins to flower, the production of new leaves slows, and existing leaves often develop a bitter flavor. Removing flower spikes immediately upon sight can temporarily delay this process and prolong the harvest period.
Harvesting Techniques for Sustained Production
To achieve maximum yield and encourage a bushy growth habit, harvesting should utilize two primary techniques: individual leaf selection and strategic stem pruning. When picking individual leaves, focus on the mature, fully developed leaves found lower down on the plant. These leaves are typically larger and contain the most concentrated flavor compounds.
Pinching off mature leaves promotes better air circulation and light penetration, supporting the development of younger foliage. When removing a leaf, use your fingers or clean shears to snip the petiole close to the main stem, ensuring the stem itself is not damaged. This method allows for frequent, small-scale harvests without stressing the entire plant.
For increased overall production, employ the technique known as “pinching back” the apical meristem on the main stem. The apical meristem is the primary growth point at the top of the stem, which suppresses the growth of side shoots. Pinching the main stem just above a set of leaf nodes removes this growth point, encouraging the plant to divert energy into the dormant lateral buds below.
Removing about a quarter to a third of the top portion of the stem will cause the plant to branch out, resulting in multiple new stems and a greater number of leaves. A good rule of thumb is the “one-third rule,” meaning you should never remove more than one-third of the plant’s total foliage at any single time. This conservative approach ensures the plant retains enough leaf area for efficient photosynthesis to recover quickly and continue producing.
Post-Harvest Handling and Preservation
Immediate and careful handling of harvested perilla leaves is necessary to retain freshness and minimize quality degradation. After picking, the leaves should be gently washed in cool water to remove any dirt or debris. Avoid rough handling, as the delicate leaves can bruise easily, leading to brown spots and accelerated wilting.
Thoroughly drying the leaves is a crucial step before storage, as excess moisture encourages bacterial growth and spoilage. A salad spinner provides a quick and effective drying method, or the leaves can be spread in a single layer on clean paper towels and gently patted dry. The goal is to remove all surface water without crushing the leaf tissue.
For short-term storage, ideal for fresh consumption, the leaves should be cooled quickly to remove field heat. Place the dried leaves in a sealed plastic bag or an airtight container layered with a slightly damp paper towel. Storing them in the refrigerator, ideally in the crisper drawer, helps maintain humidity and keeps the leaves fresh for up to a week. For longer preservation, perilla leaves can be frozen by briefly blanching them, or they can be dried completely for use in teas or spice mixtures.