Shiso, also known by its botanical name Perilla frutescens var. crispa, is a highly utilized herb in Japanese cuisine. It is an annual plant that thrives in various climates and is a staple for anyone interested in Japanese food. The herb is part of the mint family, Lamiaceae, and is native to the mountainous regions of China and India, but is now cultivated worldwide.
Types of Shiso
There are essentially two main types of shiso: green and red. These varieties are distinguished by the color and morphology of their leaves, though coloring can also extend to the stalk and flower buds. The redness in shiso is attributed to shisonin, an anthocyanin pigment found in perilla.
Red Shiso (Akajiso)
Red shiso, botanically referred to as f. purpurea and f. crispa for its ruffled form, is primarily used in the preparation of umeboshi (pickled plums) to impart a distinct red color. The leaves turn bright red when steeped in umezu, the brine resulting from plum pickling. Red shiso can also be used with umezu to create certain types of sushi. Due to its slightly bitter taste when raw, red shiso typically undergoes salting or blanching before consumption. It can also be dried and pulverized into flakes, mixed with salt to create a seasoning known as yukari, an ancient term for the color purple.
Green Shiso (Aojiso / Ōba)
Green shiso, also known as f. viridis and f. viridi-crispa for its ruffled form, is the more versatile variety for culinary applications. It is commonly used as a garnish for various dishes, including noodle dishes like hiyamugi and sōmen, meat dishes such as sashimi and tataki, and tofu dishes like hiyayakko. Whitebait (shirasu) sashimi is frequently garnished with green shiso. The leaves can also be used whole as receptacles for wasabi or other garnishes, battered and fried to make tempura, or chopped to flavor fillings and batters for warm dishes. In Japan, green shiso is sometimes used as a topping for pasta, often combined with raw tarako (pollock roe), and has even been used in pizza toppings as a substitute for basil.
Other Varieties of Shiso
Beyond the common green and red types, several other forms of shiso exist, defined by their leaf characteristics:
- Bicolor shiso (f. discolor): Features leaves that are green on the top side and red on the back side, with a flat surface.
- Variegated shiso (f. rosea): Displays a mixture of both green and red colors on both sides of its leaves.
These varieties, while differing in appearance, do not significantly vary in their culinary properties.
Botanical and Horticultural Information
Shiso belongs to the genus Perilla, which is considered monotypic, meaning it contains only one species, Perilla frutescens. However, within this species, there are recognized varieties and forms. The botanical name for shiso is Perilla frutescens var. crispa. It is sometimes mistakenly referred to by its genus name, Perilla, which can also apply to a different cultigen, Perilla frutescens var. frutescens.
Shiso plants typically grow to a height of 40-100 centimeters (16-39 inches). They possess broad, ovate leaves with pointed ends and serrated margins, arranged oppositely on long leafstalks. The plants are not frost-hardy and prefer warm to hot climates.
Cultivation and Germination
Shiso seeds are known for their toughness. While they can be sown directly in the garden, germination may be slow, taking 3 to 4 weeks, with a lower success rate. To ensure better germination, it is recommended to soak the seeds in water for 24 hours before sowing. The soaked seeds can then be sown directly, either in the garden or indoors in starter pellets like Jiffy-7s. It is important to keep the seeds moist throughout the germination process to avoid delays.
Sowing Indoors
Starting shiso indoors allows for an earlier start to the growing season. Sow seeds in Jiffy-7 pellets or other suitable starting medium. Plant as many seeds as desired plants, plus a few extra, as seedlings can be thinned out as they grow. Ensure seeds do not dry out.
Sowing Outdoors
When sowing outdoors, it is recommended to do so 1 to 2 weeks after the average last frost date, when soil temperatures are between 65°-75°F. Shiso seeds require light to germinate, so they should be pressed into the surface of the soil and not covered deeply. Spacing of 10-12 inches apart is recommended to allow for adequate growth.
The packet of Japanese seeds may suggest covering the seeds with a moist sheet of newspaper until germination, a method that can also be employed without newspaper by ensuring consistent moisture.
Growing Conditions
Shiso prefers well-draining soil but can grow in various soil types. They are not overly particular about water, requiring regular watering, especially during dry spells or when the plant begins to wilt. Plants grown in pots, however, need significantly more water due to faster soil drying.
Shiso thrives in full sun to part shade. For optimal growth, fertile, well-drained soil with a slightly acidic pH of 5.5 to 6.5 is ideal. Light fertilization and the addition of organic matter before sowing can further enhance growth.
Shiso plants are generally resilient, rarely succumbing to diseases and are not particularly attractive to most insects. They can self-seed readily in temperate climates with mild winters.
Harvesting and Usage
Leaves can be harvested at any time after the plant reaches a few inches in height, preferably before flowering. It is important not to remove more than one-third of the plant's foliage at once to ensure continued growth.
At the end of summer, flower buds form. These can either be left to develop into seed pods or clipped off to encourage continuous leaf production. Shiso seed pods, known as shiso no mi, are salted and preserved as a spice. Shiso sprouts, buds, and cotyledons are called mejiso and are used as delicate garnishes. Shiso flowers, or hojiso, are also used as garnishes for sashimi, intended to be scraped off the stalk with chopsticks and added to soy sauce dips.
Culinary Uses Beyond Japan
Shiso's unique flavor, often described as a combination of mint, basil, and a hint of cinnamon or anise, has led to its adoption in various cuisines. In Vietnamese cuisine, red shiso leaves, known as tía tô, are used in salads, soups, and stir-fried dishes, particularly with seafood. The herb's strong flavor profile makes it an excellent complement to dishes like shrimp and fish. Tía tô leaves are also eaten as a garnish with bún (rice vermicelli).
Shiso can be dried for preservation. Methods include hang drying in a dry, dark room, oven drying at temperatures below 180°F, or using a food dehydrator at 125-130°F until the leaves are brittle.
Medicinal and Other Properties
Shiso is recognized for its medicinal properties, particularly in Japanese culture, where it is believed to be effective against allergies and possess anti-bacterial, anti-inflammatory, antioxidant, and antiviral properties. Rosmarinic acid, found in shiso, is known for its anti-allergy effects. The herb is also thought to strengthen the immune system and provide beneficial nutrients like iron, calcium, and carotene.
The anti-inflammatory properties of shiso can help soothe sore throats and inflamed respiratory tracts, and it may also aid in managing stomach aches and digestive issues. Shiso tea, made from dried leaves, is consumed for its health benefits.
Potential Toxicity
While beneficial in many ways, wild shiso contains compounds, such as perilla ketone, which can be toxic to livestock like cattle and horses, potentially causing pulmonary edema. This condition is sometimes referred to as perilla mint toxicosis. The plant produces natural products like perilloxin, which is structurally based on a 3-benzoxepin moiety.
Historical and Etymological Notes
Shiso has a long history of cultivation, with mentions dating back to ancient China around 500 AD. Red shiso became available to gardening enthusiasts in England by the mid-19th century. The Japanese name "shiso" (紫蘇) originates from the Chinese name "zisu" (紫蘇), meaning "purple perilla." In Korean, it is known as soyeop or chajogi. The genus name "Perilla" is thought to have been coined by the Latin scholar Linnaeus, possibly referencing the calyx resembling a "little bag."
Harvesting purple perilla leaves to make herbal tea FullHappyBelly
