Plant Profile: Eutrema japonicum

Wasabi is a perennial herb that originates from Japan and Korea, belonging to the same botanical family as cabbage, horseradish, and mustard. It thrives naturally in the cool, moist environments of mountainous regions, often found along riverbanks and streams, where ferns typically grow.

The wasabi root serves as a substitute for horseradish, and when the rhizome is finely grated into a vibrant green paste, it becomes a beloved condiment in Japanese cuisine, known for its sharp, spicy flavor. All parts of the wasabi plant are edible, particularly the rhizomes, which require up to three years to reach a harvestable size of about one inch in diameter.

Finding wasabi plants in garden centers can be challenging, and large-scale cultivation is rare due to the plant's specific growing requirements, even under optimal conditions. However, seeds can be purchased online. The ideal time to sow these seeds is from late fall to early winter, as they need around two months of cold temperatures to germinate. Alternatively, seeds can be refrigerated for two months and then planted outdoors when temperatures are between 50 and 55 degrees Fahrenheit. To enhance germination, soak the seeds in distilled water overnight to soften their outer coating.

For successful wasabi cultivation, use organic, loose, and crumbly soil that offers good drainage while retaining moisture. Adding coarse sand can help improve drainage. The optimal temperature range for growing wasabi is between 46 and 70 degrees Fahrenheit. Seeds should be sown in shaded areas or beneath tree canopies to maintain a cool, humid environment. Plant the seeds two inches deep, spaced two inches apart in rows, and place one seed in each hole. If using containers, thin the seedlings and transplant them into larger pots that are at least 10 to 12 inches deep and wide, placing the container in a shallow water pan. A small amount of slow-release 12-12-12 fertilizer will suffice for three to four months. Ensure the plants are well-watered, but avoid letting them sit in water.

To harvest the rhizomes, gently pull the entire plant from the ground. For the best flavor, grate the cleaned roots within thirty minutes of harvesting, although they can be stored in the refrigerator for up to a month. Rhizomes can also be dried and ground for extended shelf life. Wasabi can be propagated through plantlets that develop around the main plant or by dividing the rhizomes. This plant is rich in vitamin C and also contains vitamin A and iron.

In terms of pests and diseases, wasabi can be vulnerable to aphids, alfalfa looper larvae, cranefly larvae, slugs, leaf spot, root rot, and rhizome rot. To prevent infestations and diseases, it is advisable to prune any wilted, damaged, or dead leaves.