What is Satsuma-imo (Sweet Potato)?

The sweet potato (satsuma-imo) is native to Mexico and the surrounding tropical American region. Diploid Ipomoea trifida, which belongs to the family Convolvulaceae, has been identified as a wild ancestor of the sweet potato. Today’s sweet potatoes are believed to have been developed through artificial selection as a result of mutation and cross breeding with wild species. Whether artificial or spontaneous, a great number of sweet potato species have been created throughout the long history of its cultivation. Different regions grow varieties befitting their geographical needs. In fact, sweet potatoes are grown in most of the tropical, subtropical and temperate zones around the glove today. For that reason the sweet potato comprises an astonishing array of varieties, with new types being developed one after another.

Contents:

• What is Satsuma-imo (Sweet Potato)?
• Advocating for Seasonal Harvest
• Root Crops
• Sweet Potato
• Purple Sweet Rord
• Cultivation of Sweet Potatoes
• Nutrition
• How to cook Satsuma-imo? (Sweet Potato Recipes)

What is Satsuma-imo (Sweet Potato)?

Advocating for Seasonal Harvest

People used to coexist more closely with Mother Nature and conducted their lives by adapting to the changing seasons. Thus the seasonal harvest is a kind of food culture based on coexistence with nature. A diet consisting of foods created by nature through the four seasons of spring, summer, autumn and winter contributes to a lifestyle that matches the human biorhythm. Organically grown seasonal produce protects our life and health and enriches our way of living.

Spring is the season to harvest sprouts, leafy vegetables, stem vegetables and flowering vegetables. Eating these vegetables in spring helps promote our metabolism, which is relatively slower during the winter. Bitter-tasting alkaloid, plentiful in sprouts and flowering crops, promotes cell division.

Summer is the time when “hanging” vegetables hit the market. The summer heat could disturb metabolism and harm one’s health. Hot summer weather could make you consume too much water and salt, which would strain your heat and cause high blood pressure and swelling. The potassium abundant in hanging vegetables helps the body excrete salt while it speeds metabolism. Vitamins A and C prevent the fatigue due to summer heat.

Autumn is the colorful harvest season that produces yellow and green vegetables, root crops and globular leafy vegetables. This season offers a wide selection of seasonal harvests such as persimmons, pears, tangerine oranges, chestnuts and matsutake mushrooms.

Winter is the season of root crops and leafy greens, above all else. Daikon radish, for example, aids in the digestion of starchy carbohydrates and proteins. It’s a savior for often overworked stomachs during the winter season of holiday parties. Pumpkin, wild yam and sweet potato, which give strength and stamina to the body, are believed to prevent one from catching a cold when they’re consumed in midwinter. Mitsuba (an herb commonly known as Japanese parsley), shungiku (garland chrysanthemum) and spinach cleanse the blood as they neutralize and detoxify substances that inhibit cells, thereby helping to build strong body that’s tolerant to cold.

Root Crops

Root crops are excellent vegetables, often called the treasure house of nutrition. Many root vegetables are harvested during autumn or winter. Crops that store nutrition in roots under the soil include daikon radish, turnip, carrot, gobo (burdock root) and sweet potato. Those that store nourishment in underground stems include lotus, potato and taro root. Examples of edible underground bulbs made of transformed leaves are onion, garlic and rakkyo (scallion).

Potatoes, which make up the majority of root-crop production, and globular leafy vegetables complete their life cycles as they produce seed potatoes or bulbs and the above-ground parts of the plants die. These plants, if left unattended, will bud on their own when the next season comes and can again be harvested as root vegetables. If the plants are replanted elsewhere by human hands, they will also bud eventually. Root vegetables stay alive and can be stored for long periods. If stored properly they can be eaten throughout the year.

Potatoes and sweet potatoes are foods that are considered a staple diet in some countries. Sweet potatoes, in particular, carry such special meaning for Japanese people that they evoke emotional sentiments and hear-warming scenes.

Sweet Potato

The sweet potato was introduced in Japan in about 1609, and cultivation began in Ryukyu and Satuma. Growing techniques were then improved, and a technique similar to that used today was developed in the middle of the Edo period. Sweet-potato cultivation subsequently spread to the Kanto region. The story of sweet potatoes saving people from famines is well known in Japan.

Breeding techniques for crop improvement have advanced significantly during recent years, in which there has been a sharp rise in demand. These techniques have been used to develop many new varieties of sweet potato. The mega-hit varieties are “Beni Azuma” and Koukei No. 14, also known as “Kintoki.” These two are the most popular sweet potatoes among many varieties, accounting for more than 50 percent of all sweet potatoes sold as fresh produce in Japan today.

Purple Sweet Rord

The color of the purple sweet potato comes from anthocyanin, known to provide antioxidant and anti-mutation properties and help prevent high blood pressure. For that reason, products made from processed purple sweet potatoes have been developed and manufactured in increasing numbers. However, the purple sweet potato has little sweetness so it isn’t suitable for consumption as fresh produce. This has created a mission to develop new varieties.

The “Purple Sweet Rord” is a new variety developed by crossing a purple sweet potato from Kyushu as the female partner with the mixed pollen from multiple male plants, including Kintoki. The outside skin is deep reddish purple, while the flesh is purple. The Purple Sweet Rord was registered as Norin No. 56 in 2002. It is much more suitable for eating than conventional purple sweet potato varieties and provides a better yield.

This variety of purple sweet potato is grown in North Carolina (albeit in small amounts), Where it’s simply called “Purple.” Nijiya Farm seems to have all the conditions required to grow tasty sweet potatoes. We can think of many such conditions, but the first is that our farm has the ideal climate for sweet potatoes because it’s located close to the native origin of this plant. The farm gets very little rain, which makes it possible for us to control the amount of water supplied to crops. The soil is right for sweet potatoes, and the variety we grow is well suited to the soil. Above all else, Nijiya Farm provides the environmental conditions in which organically grown plants can thrive as healthy, strong crops.

Cultivation of Sweet Potatoes

In January, seed potatoes are “laid” into trays or some sort of container in which to grow many seedlings. In or around June, the seedlings are planted in the fields as if one were planting a cutting from a tree. The planted seedlings are well irrigated and grow numerous stems that look like vines. Then, the chlorophyll in the leaves increases carbon anabolism. Sunlight, water from underground and the carbon dioxide in the air synthesize carbohydrates (or starch), which helps leaves, vines and roots grow and make sweet potatoes.

Once the stems and leaves above ground grow to a certain size, the characteristics of this short-day plant cause the first root from the rootstock to store nutrition. This root swells and turns into potatoes when the plant’s water content reaches a certain level and a certain temperature is reached. The same process occurs with the second, third and subsequent roots.

Some of the sweet potatoes harvested are stored as seed potatoes, which will be used to initiate the next year’s cultivation. The sweet potato, although it is a flowering plant, doesn’t go through the same process of blossoming, pollination and fruit bearing the way that fruit vegetables generally do. It’s a wonder plant that neither passes pollen from the stamen to the carpels nor grows seeds but continues to multiply according to its DNA programming.

Although flowers aren’t commonly associated with sweet-potato cultivation, the Purple Sweet Rord grown at Nijiya Farm blooms with many flowers that look likes morning glories. Abundant flowering has no direct connection with harvesting but is proof of the perfect environment our sweet potatoes have for their growth.

Nutrition

Even when steamed or baked, Purple Sweet Rord maintains the sweetness unique to a sweet potato and remains moist and delicious. Its flavor can surpass that of the Kintoki sweet potato. Because of its beautiful color, Purple Sweet Rord is also great as an ingredient for processed foods. The sweet potato is rich in nutrients that are otherwise hard to get as part of our daily diet. In fact, it’s said that eating a sweet potato a day can prevent all adult diseases. The nutrients in sweet potato include a high amount of dietary fiber; sucrose (which helps regulate intestinal function); vitamin C and other vitamins that are resistant to heat; beta carotene; pantothenic acid; folic acid; and many mineral unique to root vegetables: calcium, iron, magnesium, phosphorus, potassium and zinc. Purple Sweet Rord is also rich in anthocyanin, an antioxidant created when beta carotene turns purple. Thus it’s believed to encourage blood circulation.

The basis of organic growing lies in accepting Mother Nature as she is, encouraging the unique characteristics and growing ability of each plant, and maintain and promoting the endless cycle of nature. That makes it possible for us to harvest crops without losing their natural flavor and nutrition, and to enjoy the blessings of each season to the fullest.

How to cook Satsuma-imo? (Sweet Potato Recipes)

Gochiso Magazine, Nijiya Market