How to plant wasabi

Wasabia japonica

Wasabi, also known as wasabia and Japanese horseradish, is a plant native to Japan, grown mainly for use of its thick underground stem (rhizome), but which is often incorrectly called the root. When grated, its rhizome has a very spicy flavor, similar to horseradish, but not identical. Its leaves can also be eaten and taste less spicy than the rhizome.

Much appreciated in Japanese cuisine, its cultivation is also increasing in the West, mainly because Japanese wasabi production does not even meet its own domestic demand. However, it is considered a difficult plant to grow.


Japanese wasabi or horseradish grows well in cold and humid climates. Ideally, the temperature remains between 8 ° C and 20 ° C. Places with temperatures above 28 ° C are considered unsuitable for cultivation. In regions where the temperature drops below -3 ° C, the aerial part of the plant dies, but it can still survive and regrow when the temperature is adequate again.


This plant grows best in partial shade, although it can also be grown in direct sunlight in regions where the climate is mild even during summer.

Cultivation systems

There are two traditional systems of growing this plant. The most used in Japan is cultivation in a semi-aquatic environment, with a smooth and continuous flow of cold water. In Japan it is common to plant beds of rocks made along water courses or in tanks. Each bed is made up of a thick layer of small rocks on which there is a layer of gravel, which in turn is covered with a layer of a few centimeters of sand.

The other system is cultivation in places with moist soil, rich in organic matter, usually under large trees that provide shade and help to keep the environment moist. In this system, the soil must retain water well, remaining constantly moist, but it should not be soaked or flooded. Wasabi grows well in running water, with good oxygen concentration, not in soil flooded with stagnant water.

Another alternative is cultivation in hydroponic systems. The pH of water and soil must be between 6 and 7, whatever the cultivation system employed.


Japanese wasabi or horseradish is usually grown from sprouts or seeds. It is also possible to use pieces of rhizomes, but this is less common.

The seed propagation method is not the most appropriate when it is expected to harvest rhizomes, as plants from seeds often do not produce good rhizomes. When the aim is to commercially harvest rhizomes, planting should be done using only plant shoots that produce rhizomes of excellent quality.

When a plant is harvested, its shoots are removed and used to propagate the wasabi. So often harvesting and planting are carried out at the same time, as the largest shoots can be planted directly at the final location. The smallest can be planted in pots left on trays of water, so that the soil of the pot is not dry. The shoots must have a healthy appearance and be at least 4 cm high and at least 4 leaves. There may be up to 20 sprouts suitable for propagation in each plant at the time of harvesting the rhizomes.

The seeds do not normally germinate if they do not go through a long period of low temperatures. So it is necessary to leave the seeds in a refrigerator at 5 ° C for two months to break the dormancy before sowing them (the time needed may vary, depending on the variety grown). Sow seeds, modules, trays and other containers, at least 10 cm high, and leave the seeds covered with 1 cm of soil. Germination occurs in approximately three weeks.

When the seedlings are at least 4 leaves and 5 cm high, which takes 4 to 6 months, they can be transplanted to a bed with partial shade. Leave the seedlings 5 ​​cm apart, with the crown 1 cm above the soil surface. About two months later, the seedlings will be approximately 10 cm high and can be transplanted to the final location.

The rhizome pieces are placed in containers containing soil or sand, kept constantly well moist, preferably with an ambient temperature of around 10 ° C. The shoots can take two months to start to appear, and when they are 4 or 5 leaves, they can be cut from the rhizome and transplanted as indicated in the previous paragraph.

At the final location, the plants can be spaced a distance of 30 cm. When performing the transplant, leave the crown about 1 cm above the soil surface.

Wasabi can be grown in pots, which must be at least 30 cm in diameter and height so that the plant can achieve good development. Leave a shallow container of water under the pot to keep the soil moist at all times.


Remove invasive plants that are competing for nutrients and resources, especially when planting in the soil. In semi-aquatic systems there are less problems with invasive plants.


The harvesting of wasabi or Japanese horseradish can generally occur 18 to 24 months after planting, when the rhizome is 3 to 5 cm in diameter and 10 to 20 cm in length. However, sometimes the plant keeps growing for up to five years before the harvest is done.

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