Wasabi

Photo: Qwert1234 — CC BY-SA 3.0 · source

Survives zone 7 through 9

Harvest calendar

Ripens: Rhizome takes 2–3 years to reach harvestable size

Best planted in early spring after your last frost, or in fall before the ground freezes, depending on your climate.

The true source of Japanese wasabi paste — most of what's served as "wasabi" outside Japan is actually dyed horseradish, since real wasabi is slow-growing, exacting to cultivate and expensive. Grated fresh rhizome loses its sharp, complex heat within about 15 minutes, unlike horseradish's more stable pungency.

Hardiness

Zone 7–9

Habit

Herb

Edible part

Root, Leaf

Ripens

Rhizome takes 2–3 years to reach harvestable size

Mature size

Low clump to about 30–45 cm

Light

Deep to part shade

Soil pH

6.0–7.0

Environment

Cool montane stream banks

Native range

Cool, shaded mountain valleys of Japan and Korea, growing wild in the gravel beds of fast-moving streams and in shaded forest seeps.

Status

Both wild and cultivated

Years to fruit

2–3 yrs

Growth speed

Very slow — the defining fact about the crop, and the reason for its price

Spacing

30 cm (12 in) apart — about 11 per m² (10 per 10 sq ft)

Leaf shape

Long-stalked, rounded to kidney-shaped bright green blades 8–20 cm across with finely scalloped edges, in a loose rosette — the leaves and stalks are edible and pleasantly hot, and are sold in Japan in their own right.

Root system

Slow-growing rhizome, the part harvested, taking 2–3 years to reach usable size.

Fruit description

Not a fruit crop. Small white cress flowers on a spring spike give slender pods; the flowering stalk is itself eaten pickled. The crop is the thick green rhizome, grated fresh — and it loses its heat within about fifteen minutes of grating, which is why real wasabi is grated at the table.

Propagation

Division of the offset plantlets that form around the base of an established plant, or rhizome division.

Pollination

Insect-pollinated and self-compatible, but irrelevant to growing it: the crop is a rhizome, and plants are propagated clonally from offsets to keep the type.

The edible parts listed above are a starting point, not a field guide. Identify a plant with certainty — ideally against a local authority — before eating any part of it, and read the full disclaimer. Spotted something wrong? Report it.