How To Grow Perilla Leaves

Trust the Japanese, who make a virtue of dining on poisonous pufferfish, to incorporate dangerous, mint-like perilla leaves (​Perilla frutescens​ var. crispa) into their diet — but it isn't just them. Known as "shiso" in Japanese, "si zu ye" in Chinese and "kaennip" in Korean, perilla is highly regarded all over Asia for its culinary value and medicinal properties, not the least of which being the fact that it is an antidote for seafood poisoning. This may be one reason it's a mainstay of Japanese cuisine. If you go to a Japanese restaurant that offers pufferfish, don't be surprised if it comes garnished with shiso leaves, and be sure to wait until you've finished the main course before you eat them.

The peppery member of the mint family (Lamiaceae) grows in a bush from 1 to 3 feet tall and has luscious green leaves with serrated edges that are sometimes tinged with purple coloration. The leaves can also be almost entirely red, which the Japanese call "akajiso" (red shiso) as opposed to the more mild-tasting "aojiso" (green shiso) leaves. They are used as coloration when pickling plums to make what the Japanese call "umeboshi," a traditional, medicinal food that staves off winter illnesses.

You can also grow ​Perilla frutescens​ 'Purple Shiso' for its edible leaves, although this cultivar more commonly is grown as an annual with brilliant purple leaves. Regardless of species or cultivar, the perilla plant is a tender annual and does not tolerate cold, but it grows during the summer throughout North America, where the red variety in particular is known as the beefsteak plant.

Perilla leaves are common in Asian cuisine in general, but the Japanese variety is smaller and slightly mintier than the Korean one. In Japanese cuisine, shiso is often used as a garnish and eaten raw, especially with sushi, whereas in Korea, kaennip is more often incorporated into cooked dishes. Koreans also use oil extracted from perilla seeds, which is high in omega-3 fatty acids, as a substitute for sesame oil. This oil can also be used as a fuel source and as a base for paint and lacquer, and because it's 2,000 times sweeter than sugar, it can be used to produce alcohol for perfumes.

Perilla is attractive enough to serve as an ornamental in a flower or herb garden, and it has been cultivated in North America for its showy green and purple leaves for many years. Its flowers aren't particularly notable, but the bushy plant exudes a pleasant minty fragrance that more than makes up for the lack of coloration of the flowers and, as a bonus, keeps deer away. Because it's a self-seeding plant that reproduces prolifically, it escaped cultivation to grow in the wild, where it is considered in some places to be an invasive and noxious weed. In these places, you can still grow perilla indoors in containers to adorn a window well or some other sunny spot.

Among their health benefits, perilla leaves act as an anti-inflammatory, and shiso has been recommended by Japanese health practitioners to treat illnesses such as asthma, arthritis and eczema. The leaves are a tasty addition to salads, conferring a complex taste with hints of cumin, mint, ginger and pepper, and they are rich in vitamin A, calcium and iron. The omega-3 oils derived from ground seeds reportedly are good for the heart. The perilla plant is very easy to grow, and chances are that you'll find it in a nearby field, but even if you do, there's nothing like growing it yourself.

You can harvest shiso seeds yourself, but one problem with this approach is that seeds don't keep well in storage, so you may want to obtain them from a commercial supplier. You can direct-sow seeds outdoors in moist, well-draining soil when nighttime temperatures stay above 45 degrees Fahrenheit, but if you want to get a jump on the growing season, consider starting seeds indoors.

Perilla seeds take from seven to 21 days to germinate at a temperature of 70 degrees, so to have seedlings large enough to transplant at the beginning of the growing season, you should sow them in seed-starting mix four to six weeks before the last frost in spring. Soak seeds in water for 24 hours before sowing them and sow them 1/4 inch deep, covering them lightly with soil. To ensure they have the light they need to grow, keep them under grow lights until they are ready for transplanting.

When planting seedlings in the garden, space them 10 to 12 inches apart and keep the soil moist but not wet. Perilla seeds are vulnerable to fungal infections that cause damping off, so avoid overwatering.

Perilla leaves will grow in zones 2 through 11, which is just about everywhere, but it's a warm-weather annual plant. It's native to the Himalayas, so it can definitely tolerate cool summers. Dappled shade is recommended in areas with particularly hot summers, but in areas with cool summers, perilla should get six to eight hours of direct sunlight a day.

Transplant perilla seedlings outdoors in spring after the last frost when the soil temperature stays above 45 degrees and the air temperature is about 68 degrees. Perilla cannot tolerate frost or cold and can easily die if temperatures drop below its comfort zone, but it loves heat and can tolerate drought. When in doubt, it's best to wait a little longer in spring to be sure temperatures have stabilized before planting seedlings or direct sowing seeds.

Perilla, or shiso, isn't finicky about soil composition, but it prefers well-draining soil with a constant supply of moisture. It grows best on slightly acidic soil with a pH between 5.5 and 6.5, so prepare the soil by turning in plenty of compost and other organic material and side-dress the growing plants with compost tea or diluted fish emulsion every three to four weeks during the growing season.

In most climate zones, you should grow shiso in full sun, but in areas with intense summer heat, partial shade is recommended to keep the leaves from drying out. Water moderately to keep the soil moist but not wet. Shiso is moderately drought-tolerant, so if you skip a watering every now and then, it shouldn't be a problem.

Perilla is a self-seeding annual that flowers in late summer or early autumn, and the flowers produce seeds near the end of the growing season. If you let this occur naturally, the plant will propagate itself far and wide and become a weed, so it's best to pinch off the flowers before they go to seed. If you want to collect seeds, leave one or two flowers and wait for them to dry out and turn brown. Then, take them inside and shake them into a paper bag. The seeds are fragile and need to be stored in a dry place at a low temperature to ensure viability the following year.

Pinching back the growing tips of the stalks encourages the plant to grow bushier, and leaves can be harvested as soon as they are big enough. You can harvest leaves throughout the growing season even when the plant is small, and doing so encourages the bush to produce more. Rather than picking off leaves one by one, pinch off a sprig just above the junction of a pair of leaves. This helps train the plant to grow bushy instead of rangy.

Perilla is not particularly susceptible to insect attacks, but its luscious green leaves are bound to attract some of the usual suspects.

• ​Aphids​ are the tiny creepy crawlies that congregate on the underside of the leaves and produce a sticky deposit known as honeydew. Not only does this substance ruin the leaves but it also promotes the growth of sooty mold that can spread to other leaves and may infect the whole plant. You can wash off the aphids with water or treat the plant with insecticidal soap.
• ​Cutworms​ live in the soil and attack young seedlings, often severing the stalks in half. To keep them away, make collars by cutting the bottoms out of plastic coffee pods. Put one around each seedling. Remove weeds because that's where cutworms lay their eggs.
• ​Spider mites​ are a little bigger than aphids, and they suck the juices from the leaves, producing whitish spots that make the leaves unusable. As you do with aphids, you can spray these off with water or control them with insecticidal soap. Hot pepper wax will also control them and keep away deer and rabbits as a bonus but be sure to wash the leaves well before eating them.

Because perilla likes to grow in slightly moist soil, it isn't as vulnerable to bacterial and fungal diseases as many other plants, but occasionally, some problems may occur.

• ​Damping off​ is caused by a fungal infection and can prevent seeds from germinating or can cause young seedlings to wilt and die for seemingly no reason. It occurs when the soil is too wet or it contains too much nitrogen and the air temperature is above 68 degrees. Avoid it by refraining from overwatering or overfertilizing and provide plenty of space between seedlings so air can circulate.
• ​Downy mildew​ creates gray patches on the underside of the leaves and makes them unusable. You can also control this disease by spacing seedlings to allow air to circulate. When you water the plants, water the roots only and avoid getting the leaves wet.
• ​Rust​ is caused by a number of fungal diseases, and it leaves rust-colored deposits on the leaves and stems. Remove infected plants and avoid planting in that location the following season.