How to Grow Shiso Herb from Seed

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Growing Shiso

Shiso, native to the Himalayan mountains and China, was introduced to Japan where it gained popularity. It may be considered a perennial and annual both, depending on the zone in which its planted along with weather conditions. It is a part of the Lamiaceae (mint) family and naturally repels most insects because of this. Shiso may be used for medicinal purposes, particularly in Japanese culture, for its effectiveness against allergies and for having anti-bacterial, anti-inflammatory, antioxidant, and antiviral properties. Shiso is effective against allergies as it contains rosmarinic acid. Rosmarinic acid suppresses certain allergic and inflammatory responses, making it a potentially helpful aide in controlling allergies.

How to Grow Shiso from Seed

• Soak the seeds in water for 24 hours prior to sowing seeds
• It should be planted in temperatures of 45°F or warmer
• Sow seeds ¼” into soil without covering

To grow shiso from seed, it is recommended to soak the seeds in water for up to 24 hours before sowing seeds and then to sow them directly after following removal from the water. Shiso should be planted after the threat of frosting has passed and outside temperatures are moderate, preferably warmer than 45 degrees F. Plant only a few seeds at a time, up to 3, given that shiso grows up to heights of 1 foot wide and 3 feet tall. Sow the seeds in fertile, well-drained soil, only 1/4" into the soil and leave it uncovered as shiso requires light to germinate. Space the plants 10-12" apart to ensure that they have enough room for growth. Shiso needs full sun to grow, especially in its earliest stages as it needs light for germination. Shiso takes 7-21 days to germinate.

Shiso Soil

Shiso prefers soil that is fertile and well-drained, with a more acidic pH of 5.5 to 6.5. However, shiso will grow in average soil conditions. For ample growth, lightly fertilize the soil and add organic matter into the soil before sowing seeds. This will allow the shiso to flourish as it enjoys the extra nutrients provided by fertilization and organic matter. Shiso does not require mulching, given that the soil is maintained to be moist. It may be defined as needing a medium amount of water but be careful to not make the soil too moist particularly in its early stages of growth, as the seedlings are known to be prone to damping off. Damping off, caused by wet conditions, may cause seedlings to be weaken or die after germination.

Watering Shiso

• Prefers regular and consistent watering
• Requires up to 1” of water a week
• Make sure that the soil stays moist

Shiso prefers regular and consistent watering, just enough to keep the soil moist. It requires a moderate amount of water, up to 1" a week given that rainy weather conditions are not present. Shiso prefers warm to hot climates as it is not a cold hardy herb, and may require more frequent watering depending on the humidity levels outdoors in the zone it is planted in. If its soil is struggling to retain moisture, consider spreading mulch on top of the soil to lock in its moisture. Regularly check its soil with fingertips to ensure that it is not too dry. If it feels dry on the surface, it is time to water it.

Is Shiso A Perennial?

Shiso is a perennial but may be grown as an annual in certain climates. In areas with heavy winters, it may be grown as an annual as it is not cold hardy and will not withstand freezing temperatures or anything beyond light frosting. Particularly in USDA zones 11 and above, Shiso is grown as a perennial and is often considered to be perennial due to its ability to self-seed.

Shiso in Winter

• Is not cold hardy
• Does not tolerate freezing temperatures
• May need to be transplanted to indoors

Shiso is not a cold hardy plant and because of its intolerance to wintry conditions, may be grown as an annual in some areas while it is a perennial by definition. It is not known for being able to thrive outdoors in the winter, but rather needing to be transferred to a pot indoors under a bright grow light. If left outside in temperatures under 45°F for a prolonged amount of time, shiso will die back to the ground as it does not sustain such temperatures well. If transferring shiso indoors during winter, make sure that the pot it is being transferred to is big enough for its potential growth of 3 feet tall and 1 foot wide.

Growing Shiso in Pots

Shiso grows well and can thrive in pots and other containers. It is recommended to choose a container that is at least 6 inches deep and wide when initially planting, but you will likely need to transfer it to a larger pot within time if you decide to keep it inside for the duration of its life cycle. It is best to keep shiso in a pot indoors if the threat of winter or wintry weather conditions is present. Shiso does not usually tolerate winter weather conditions and is expected to die back in colder conditions than it is tolerant of, usually below 45°F.

How to Care for Shiso Plants in Pots

• Make sure that it receives full sun
• Make sure that it receives a moderate amount of water
• Check the soil’s moisture levels frequently

To care for shiso in pots, make sure that it receives enough sunlight and water. Shiso prefers full sun and moderate watering. Since pots are known to dry soil quickly, check the soil frequently for moisture levels as dry soil can make or break the plant. Potted plants may need watered more often than if they were planted in-ground.

Growing Shiso Indoors

Shiso may be grown indoors or outdoors but is most often grown outdoors due to its growth ability of 3 feet tall and 1 foot wide. However, it is most often grown indoors if threatened by winter weather conditions or a frosting as these conditions are likely to kill the plant. In such conditions, shiso is easily transferred to a plant and grown indoors. It is not terribly fussy about its growing environment or soil given that it receives enough sunlight up to 6 hours a day and moderate watering of its soil. Make sure, if you are planting it in a pot, that it has enough drain holes to maintain well-drained soil.

Shiso Companion Planting

Shiso is a good companion plant for tomatoes and its flowers are highly attractive to pollinators. These flowers usually appear in the late summer and early fall. Shiso also does well planted next to herbs that contain consistent moisture level such as basil and parsley. Since shiso naturally repels insects as it a part of the mint family, it does not attract any and will not cause harm to other plants near it in this regard. However, shiso may be apt to get Downey mildew. For this reason, it is important to ensure that it has ample space in the garden and is not overwatered.

Shiso Flowers

Shiso flowers are popularly used in Japanese culture for everything from medicine to food. It is used in culinary dishes such as soups, salads, with tofu, fried and more. Shiso may be known by their different varieties: green and red. It is said that the red leaf varieties are milder than the green and have a minty flavor. In appearance shiso flowers are just as unique as their flavor. Shiso may grow in green and red varieties, but its flowers are almost always a light purple hue upon blooming. These flowers grow up the stem diagonally on each side of it, initially sprouting buds that may be similar to lavender in look. The fragrance of the flowers has been described as being earthy and slightly spicy.

Harvesting Shiso

Shiso may be harvested best with scissors or shears to cut the growth evenly. When harvesting shiso, much like other plants it is important to not remove more than 1/3 of its overall mass at one time as this will hinder its future growth. Shiso flowers and leaves may also be hand-picked if scissors are not available, but it is best to use scissors or shears as these will ensure that the cut is clean, attractive and does not damage the plant which could happen from pulling on it.

When to Harvest Shiso

• When its flowers have bloomed/strong>
• When 1/3 of its overall mass may be harvested safely
• During late summer to early fall months

Drying Shiso

Shiso is used in a multitude of culinary dishes across the world, popularly Vietnamese summer rolls and in a frozen dessert called granita. Its dried leaves are also commonly dried and ground to be used as seasoning on rice, omelets, and soups. Shiso tea, created by steeping its dried leaves, is consumed for its anti-inflammatory, allergy-fighting, and antioxidant properties. It is known to help strengthen the immune system and its usage is popular in Asian countries and cultures for the treatment of common ailments. Shiso is also known to be high in iron, calcium and carotene.

How to Dry Shiso

Hang Dry: Shiso may be hang dried by tying its sprigs and placing them in a paper bag, then hanging it from a surface in a dry, dark room. It may take up to 1-2 weeks to fully dry.

Oven Dry: To oven dry shiso, place the leaves on a try while the oven preheats to a temperature less than 180 degrees F. Once the oven has finished preheating, place the tray in for 2-4 hours, making sure to leave the door slightly ajar so that they do not cook but rather dry out.

Food Dehydrator: To dehydrate shiso in a food dehydrator, preheat it to 125-130 degrees F. While the food dehydrator is preheating, place the leaves on the drying rack and when it is done, place them inside the dehydrator. Keep the shiso in the dehydrator until the leaves look completely dehydrated and brittle. This can take hours as it is drying on such a low temperature.

Types of Shiso

There are two most commonly known types of shiso, green and red (purple). However, in total there are around 6 varieties. These varieties are as follows: red shiso (F. purpurea), ruffled red shiso (F. crispa), green shiso (F. viridis), ruffled green shiso (F. viridi-crispa), bicolor shiso (F. discolor), and variegated shiso (F. rosea). The names leave little up to imagination of their descriptions. Red shiso is the most commonly known from of shiso, as it growns red to purple leaves and its appearance is distinctive. Ruffled red shiso's only different is that it has a ruffled surface. The very same with green shiso and ruffled green shiso, there is only a different in the texture of their leaves. Bicolor shiso has green colored leaves on one side, with red coloring on the other, while variegated shiso has a mixture of both green and red colors on both sides of its leaves. Shiso does not differ much in its varieties, besides minimal aspects such as texture and color.

Benefits of Shiso

Shiso is known to be an anti-inflammatory, anti-allergy, antiviral, antioxidant, and antibacterial herb. It packs quite a punch on its effect of the human immune system, strengthening it beyond its normal capacities along with providing extra iron, calcium and carotene upon consumption. Shiso is also known for its positive effects on the respiratory tract as its anti-inflammatory properties can soothe a sore throat or inflamed respiratory tract. It may also be effective in controlling stomach aches and digestive issues. Shiso has been used as an herbal remedy for centuries in Japan and other Asian cultures for these properties and its unique flavor upon brewed into a tea, tincture, or eaten as is.

Additional Information on Shiso Herb

• Shiso Wikipedia Page
• Read the Best Practices for Planning Your Herb Garden!
• Learn About Hardiness Zones

Explore these Shiso Herb Seed Varieties:

• Green Shiso Herb Seeds
• Purple Shiso Herb Seeds