Shiso Is the Leaf That Paints Umeboshi Red

Open a bento box anywhere in Japan and you will probably find a small red plum resting on the white rice. Open a plate of sashimi and you will find a green leaf under the fish, working quietly as a plate, a garnish, and a divider all at once. The plum and the leaf are the same story, and shiso is the thread that ties them together. The leaf is shiso, and the red plum owes its colour to it.

Shiso is the Japanese name for Perilla frutescens var. crispa, a herb in the mint family. Shiso comes in two main forms that behave like two different ingredients in the kitchen. The green kind, called aojiso or oba, is eaten fresh and raw. The red kind, called akajiso, is a dyer and a pickler before it is ever a seasoning.

This article follows the leaf from the garden to the plate. It explains what shiso is, how its two colours divide the work, why one famous pickled plum turns red, what the leaf tastes like, and how to grow it or buy it if you live far from Japan. Shiso is a small subject with a long reach, and it repays a closer look.

What shiso actually is

The plant behind the name is a cultigen of Perilla frutescens, a herb in the mint family Lamiaceae. Its full scientific name is Perilla frutescens var. crispa. Shiso is native to the mountainous regions of China and India, but it is now found worldwide, and it grows as a perennial that is often cultivated as an annual in temperate climates. The plant reaches 40 to 100 centimetres tall, with broad ovate leaves that have pointy ends and serrated margins, arranged in opposite pairs on long leafstalks. Its seeds are tiny, about 1 millimetre across, and the plant is not frost hardy.

The Japanese name shiso comes from the Chinese zisu, meaning purple perilla, and the same root gives the Vietnamese name tia to. In Korean it is known as soyeop or chajogi. English has several names for it, and none of them quite stuck the way the Japanese one did. It is sometimes called the beefsteak plant, because purple leaf varieties resemble the blood red colour of meat. Other English names include perilla mint, Chinese basil, and wild basil. The name shiso entered the English lexicon in the 1990s, as sushi grew popular outside Japan, and today most English speakers who know the leaf at all know it by its Japanese name.

Shiso has a long history in Asia. Perilla frutescens was cultivated in ancient China, and one early mention comes from the Supplementary Records of Renowned Physicians, written around 500 AD, where it is listed as su with some of its uses described. It was introduced into Japan around the eighth to ninth centuries, and shiso has been part of Japanese cooking ever since. That is more than a thousand years of continuous use, which is a long apprenticeship for a leaf.

The red colour that makes shiso famous comes from shisonin, an anthocyanin pigment found in perilla. The pigment is the reason the red form can dye food, and it is also the reason the plant has been used as a colouring agent for centuries. When you see a deep red pickled plum or a glass of red perilla juice, you are looking at shisonin at work.

I think the first thing to understand about shiso is that it is not one ingredient but a small family of them. The green and red forms look related, and they are, but Japanese cooks treat them as different tools. One is for eating fresh. The other is for colouring and pickling. Confusing the two is the most common mistake a newcomer makes, and it is an easy one to avoid once you know what to look for.

Two leaves, two jobs

Several forms of shiso exist, defined by the colour and shape of their leaves, though colouring also appears on the stalk and flower buds. The ruffled red form was the first examined by Western botanists, and Carl Peter Thunberg named it P. crispa, meaning wavy or curly. That Latin name crispa was later retained when the plant was reclassified. The table below gives the forms a Japanese cook is most likely to meet.

The green form is called aojiso, meaning blue perilla, or oba, meaning big leaf. It is the common one, used all year round in Japanese cooking, much as basil and mint are used in Western cooking. The red form is called akajiso, and it is used mainly in pickling. In practice, if a recipe calls for shiso to be eaten raw, it means the green kind. If a recipe calls for the leaf to turn something red, it means the red kind.

There is a second perilla in Japan that is worth keeping separate. Perilla frutescens var. frutescens is called egoma in Japan and deulkkae in Korea, and its leaves are the Korean kkaennip used to wrap grilled meat. The leaves are giant and thick textured, with an intense, peppery, and earthy flavour, and they are used for side dishes and kimchi, with the seed oil used in cooking. Japanese cooks do not advise substituting it for Japanese shiso, because the two have different characteristics and different culinary uses. They are cousins, not twins.

How shiso paints umeboshi red

The most famous job of red shiso is the one that gave this article its title. Our article on umeboshi, the sour plum Japan puts in every bento quotes the line this article grew from: "The red ones get their colour from purple shiso leaves, also called akajiso, added during pickling." That single sentence hides a whole process, and the process is worth following.

Umeboshi begins as ume fruit packed in barrels with salt equal to about 20 percent of the fruit's weight. The salt draws juice out of the fruit, and the ume soak in that salty, sour liquid for about two weeks. The liquid is called umezu, often translated as ume vinegar, although it is not a true vinegar. Red shiso enters the process during the pickling stage. The leaves are salted and kneaded first to remove their bitterness, then packed in with the ume. Their pigments react with the acidic brine and dye the fruit that familiar deep red. After pickling, the fruit is laid out in the sun for several days, traditionally during the hot spell of late July and early August, and turned regularly so it dries evenly.

The pale kind of umeboshi, called shiraboshi, is made with salt alone and no red shiso at all, and under Japan's agricultural standard it is just as authentic as the red kind. The difference is purely a matter of style and flavour. The red kind carries a fresh scent from the leaves, and it is the type most people picture when they think of umeboshi. The label term shiso-zuke on a pack means pickled with red shiso, and it is one of the most useful words to know when you are choosing a pack in a shop.

The red style also has a home region. It was mainly in the Kishu Domain, as Wakayama was called during the Edo period, that umeboshi pickled with red shiso came into being, and those reddish brown to bright purple red fruits became what most people picture when they hear the word. The same tree behind the fruit is the ume, whose blossom opens Japan's year in late winter, and our article on the plum blossom that opens Japan's year before the cherry trees wake follows that flower through its season. The tree gives Japan a flower in February and a pickled plum for the rest of the year, and shiso is the bridge between the two.

I admire how little the method has changed. The ingredients are ume, salt, sunshine, patience, and leaves if you want colour. No factory trick replaces the weeks of waiting, and no shortcut produces the same result. In a food culture full of careful technique, this is almost stubbornly simple, and that simplicity is part of its charm. Shiso does not dominate the recipe. It lends its colour and steps aside.

What shiso tastes like

Describing the flavour is harder than describing the colour, because shiso does not taste like any single Western herb. Just One Cookbook calls it vibrant, herbaceous, and citrusy, with a mildly astringent taste and a bitter finish, and notes hints of mint, basil, cloves, licorice, and cinnamon. That list sounds crowded, but it is honest. The first bite is green and bright, then something warm and slightly spicy arrives, then a clean bitterness closes the taste. It is the kind of flavour that makes you pause, not because it is strong, but because it is unfamiliar.

The flavour is also why shiso pairs so well with rich food. Fatty fish like salmon, yellowtail, and tuna are the classic partners, and a leaf or two of the green kind cut through the richness the way a squeeze of lemon cuts through fried food. The same logic explains its place next to tempura and oily dishes. It is not there to be the star. It is there to keep the star from getting tired.

There is a practical side to the flavour as well. Shiso has antibacterial properties, and tradition holds that it can help slow the spoilage of raw fish and seafood. That is why it has long been used to separate different items on a platter, keeping flavours fresh and from mixing. The strips of fake green plastic grass you see in sushi trays and bento boxes are meant to replicate the leaf. They look the part, but they do none of the work, and once you know what the real thing does, the plastic version feels like a small betrayal.

I think the taste is an acquired one, and that is a compliment rather than a warning. The first time I tried it, I found the flavour odd, almost medicinal, and I understood why some people leave the leaf untouched on the plate. The second time, I noticed the citrus note. The third time, I missed it when it was absent. A herb that grows on you like that earns its place in a kitchen more honestly than a herb that impresses at once and bores by the fifth bite.

Shiso on the sashimi plate

Green shiso is most visible where it is least eaten, which is on the sashimi plate. A whole leaf often sits under the fish, and another may be used as a receptacle to hold wasabi, or as tsuma, the garnish that frames the main item. Whitebait sashimi is often garnished with the green leaf, and it appears with tataki, which is lightly seared fish, and namero, which is minced fish, and with hiyayakko, which is cold tofu. It is also used to garnish noodle dishes like hiyamugi and somen, where a few fine shreds bring aroma to a cold bowl.

The flowers and sprouts have their own roles. The flowers are called hojiso, and they are used as a garnish for sashimi. They are intended to be scraped off the stalk with chopsticks and added as flavouring to the soy sauce dip, and they can also be pickled. The sprouts, buds, and cotyledons are all called mejiso, and they are used as garnish. Red sprouts are called murame, and green sprouts are called aome. Although they are not often served in restaurants, mejiso are used as microgreens, and they carry the same flavour in a smaller, more delicate form.

The seed pods have a use as well. They are called shiso no mi, and they are salted and preserved like a spice. They can be combined with fine slivers of daikon radish to make a simple salad, and oil pressed from the seeds was once used for deep frying. Very little of the plant goes to waste, and that is a pattern you see across Japanese cooking: the leaf, the flower, the sprout, and the seed each have a job.

What strikes me about the sashimi plate is the restraint. Shiso is not piled on. One leaf, maybe two, placed with care, does the work. Japanese cooking often treats garnish as a seasoning rather than a decoration, and this herb is the clearest example I know. It earns its place by flavour and by function, and its beauty is a bonus rather than the point.

The green leaf in the kitchen

Away from the sashimi plate, green shiso is a workhorse. Whole leaves can be battered on one side and fried to make tempura, served with other fried items, and the result is airy and crisp, with the flavour concentrated by the heat. Chopped shiso is used to flavour fillings or batter for warm dishes, and they are added to mixed rice and onigiri rice balls. They go into salads, into dipping sauces, and onto pasta, where dried or freshly chopped leaves are sometimes combined with raw tarako, which is pollock roe. The leaf has even been used as a pizza topping in place of basil, and in the summer of 2009 Pepsi Japan released a seasonal flavoured beverage, the green coloured Pepsi Shiso, which tells you how far the flavour had travelled from the kitchen into popular culture.

Shiso also works in places a Western cook would reach for mint. It can be used in drinks and desserts, in recipes that call for mint, like mojitos, cocktails, ice cream and sorbets, jellies, simple syrups, and granita. Dried and ground leaves can be used as a seasoning and sprinkled on rice and noodle dishes. A pesto made from the leaves, with pine nuts, garlic, Parmesan or Romano cheese, and extra virgin olive oil, is a favourite way to use up a garden glut, and it is served with pasta, grilled fish or meat, or in a sandwich. Just One Cookbook calls shiso an all around herb, and the list of uses supports the claim. Raw, whole, or cut into fine shreds, it finds a place in almost any dish that needs freshness.

My own favourite use is the simplest one: a few fine shreds over cold noodles on a hot day. The leaf does not need a recipe to justify itself. It needs a little rice or a little noodle, something plain for it to wake up. That is the test I apply to any herb I keep in the kitchen. If it can improve a plain bowl of rice, it belongs. If it needs a complicated dish to shine, it probably does not.

The red leaf beyond umeboshi

The red leaf has a life beyond the plum jar, and it is a busy one. Red leaves are dried and pulverized into flakes, then mixed with salt to make a seasoning called yukari. The word yukari is an ancient term for the colour purple, and it was first used by Mishima Foods Co. to describe their product, though the word is now used to refer to the seasoning in general. Red leaf flakes are a common ingredient in furikake seasonings, meant to be sprinkled over rice or mixed into onigiri. A spoonful turns plain white rice pink, and children in Japan grow up with that colour on their lunch.

In Kyoto, red leaves and their seeds are used to make shibazuke, a type of fermented eggplant pickle. The leaves are also used to colour pickled ginger, the red beni shoga served with noodles and rice dishes, and to colour Kyoto style vegetable pickles. In the summer, the Japanese enjoy making a refreshing beverage called aka shiso juice, or red perilla juice, using the red leaves. It stimulates the appetite on hot days, and it is said to help with recovery from exhaustion and digestion. The leaves turn bright red when steeped in umezu, the vinegary brine left over from pickling plums, and the same colour change is what makes the juice so striking in a glass.

The Wikipedia entry on the plant gives the fullest account of these uses, and it is worth reading for the detail on each form of the leaf. The Wikipedia entry on shiso covers the varieties, the history, and the culinary uses across East Asia, and it is the best single reference for telling the forms apart. For the kitchen side, the Just One Cookbook guide to shiso is the most practical source, with recipes, growing advice, and storage tips from a cook who grows the herb herself.

What I like about the red leaf is that it refuses to be only one thing. It is a dye, a pickle, a seasoning, and a drink, and it does each job without fuss. Cooks in the West tend to sort ingredients into strict boxes, and this herb ignores the boxes. It colours the plum, flavours the rice, and refreshes the summer drink, all from the same plant. That versatility is rare, and it explains why the plant has stayed in Japanese kitchens for more than a thousand years.

Growing shiso at home

The good news for cooks outside Japan is that the plant is famously easy to grow. It is good for container growing and suitable for apartment or small space gardening, and a single pot on a balcony can supply a household through the summer. Perilla seeds are tough, so they must be softened in water overnight before sowing. Seedlings should be moved out to the garden when the nighttime temperatures are warmer than 7 degrees Celsius and all possible danger of frost has passed. If your spring is relatively cool, you may need to plant the seeds indoors for 4 to 6 weeks in mid spring.

The seeds should be planted about 6 millimetres below the surface and watered daily, since covering them with too much soil will delay germination. The ideal temperature for the plant to grow is above 20 degrees Celsius, so the timing depends on your climate. Seeds planted in May sprout about two weeks later and grow well, and leaves can be harvested as soon as they are a good size, about 3 to 4 inches long. Harvesting the leaves encourages the plant to produce more, so a few plants can keep a kitchen supplied for months.

One warning is worth keeping. Wild, weedy forms of the plant are not suitable for eating, as they do not have the characteristic fragrance, and they are high in perilla ketone, which is potentially toxic. Grow the cultivated forms from seed bought from a reputable supplier, and do not forage for the plant in the wild. The cultivated green and red forms are the ones Japanese cooks use, and they are the ones worth growing.

I have never grown it myself, but the advice from cooks who do is consistent: it is one of the easiest herbs to keep alive, and it rewards a little neglect more than a lot of attention. That suits me. A herb that needs constant care is a herb I will eventually kill, but a herb that grows in a pot with daily water and a sunny spot is a herb I can keep. If you have a balcony and a taste for Japanese food, it is a good place to start.

Buying and storing shiso

Japanese grocery stores usually carry green leaves all year round in their produce section, but you may not find them at other Asian grocery stores, and it is worth checking local farmers markets. Red leaves, however, are only available in the summer months, typically from the end of June to early July, so if you want them for pickling, call the local Japanese grocery store ahead of time to see if they carry them. There is nothing quite like the taste and texture of the fresh leaf, and unfortunately it is hard to find outside Japanese grocery stores, which is one reason growing your own is so often recommended.

Storage is simple. The best way to store fresh leaves is to cover them with a damp cloth or paper towel and put them in an airtight container or plastic bag, then place the container in the refrigerator in the crisper drawer. Use them as soon as possible, since the flavour fades with time. A leaf bought on Saturday and used on Saturday tastes noticeably brighter than one that has waited a week, and the difference is worth planning around.

If you cannot find the leaf fresh, the dried red seasoning yukari is easier to buy online and keeps well in a jar. It is not a substitute for the fresh green leaf, since it does a different job, but it brings the colour and some of the flavour to rice and noodles, and it is a good way to start. The fresh leaf is the goal, and the dried seasoning is a useful bridge until you find it.

Why shiso stays in the kitchen

A thousand years is a long time for a leaf to stay in fashion, and the plant has done it by being useful in more ways than one. It colours the plum, garnishes the fish, flavours the noodle, seasons the rice, and refreshes the summer drink. It asks for little, a pot, some water, and a sunny spot, and it gives back all summer. It is a herb that works as hard as a spice and as quietly as a garnish, and that combination is rare.

The next time you open a bento box and see the small red plum on the rice, you will know the leaf behind it. The next time you see a green leaf under the sashimi, you will know it is not a decoration. It is a small piece of Japanese cooking history, still fresh, still fragrant, and still doing its work one leaf at a time.