Eutrema japonicum
herbWasabi (Eutrema japonicum) is the true Japanese horseradish, a slow, demanding perennial of cold mountain streamsides whose pungent green rhizome is grated into the genuine condiment for sushi and sashimi - sharper, fresher, and more fleeting in heat than the dyed horseradish-and-mustard paste usually sold as wasabi. It is famously one of the hardest plants to grow well: it needs deep shade, cool temperatures, constant moisture or running water, and roughly two years for the prized rhizome to size up. The leaves, stems, and flowers are also edible and carry the same wasabi heat. A rewarding challenge for the dedicated gardener in cool, shaded, wet conditions.
Sun
full shade
Water
Every 2 days
Harvest
~20 months
to first harvest
Difficulty
hard
Lifecycle
perennial
Comes back every year
Spacing
12 in. apart
Planting Depth
Crown at soil line, kept moist
Soil pH
6.0-7.0
Soil Type
Rich, moist, gravelly
Hardiness Zones
Zones 7 β 10
When to Fertilize
Light feed through the growing season
Fertilizer
Balanced or compost; steady low feeding
Grow Wasabi in deep shade (about 75 percent shade) in rich, loose, gravelly soil that stays constantly moist but never stagnant - it is naturally a streamside plant. Keep temperatures cool, ideally between about 45 and 70F; it suffers in heat and direct sun. Plant out offsets or plugs in early spring (or fall in mild areas), spacing about 12 in. apart, and water daily or more to keep the soil saturated but oxygenated. It takes roughly 18 to 24 months for the central rhizome to reach harvest size. In zones colder than 7, grow it in containers in a cool shaded spot and protect it from freezing.
Direct sow
Apr 15
Projected first harvest
Sep 12 Β· Year 3
Year 1
Good neighbors that attract beneficial insects or deter pests
Proactive ways to stop trouble before it starts β tap a name with an arrow for its full guide
Inspect the lush leaves regularly and rinse off colonies; the cool moist conditions that wasabi needs can favor them
A constant threat in the wet, shaded bed - use grit, traps, or nightly hand-picking to protect leaves and crowns
As a brassica relative wasabi can be peppered by flea beetles - use floating row cover and keep plants vigorous
The rhizome is ready to harvest after about two years, when it reaches roughly an inch or more in diameter; lift the whole plant, cut off the rhizome, and replant the leafy offsets to start the next crop. Grate the fresh rhizome from the top down only as much as you need immediately - the heat is volatile and fades within minutes of grating, so it is always served freshly grated. The leaves, leaf stalks, and flowers are also edible with a milder wasabi bite, good pickled or in salads.
Wasabi rhizome is grated into the authentic pungent green condiment for sushi, sashimi, soba, and other Japanese dishes, prized for a clean, sharp heat that rushes to the nose and fades quickly, quite unlike the lingering burn of chili. The leaves, stems, and flowers share the heat and are eaten pickled, in salads, or as tempura. Freshly grated true wasabi is rare and valued precisely because the flavor is so fleeting.
For educational and informational purposes only β HomeSown is not medical, health, or other professional advice. Always positively identify any plant before handling or eating it; some plants, and some parts of otherwise-edible plants, are toxic. Consult a qualified professional before consuming or otherwise using any plant, especially if you are pregnant, nursing, taking medication, or have a health condition.
Year 2
Year 3