Gadenin日本語Get the appHarvest the leaves long before the rhizome
The practical consolation of a two-year crop is that you can eat from the plant in its first months. Wasabi leaves, the leaf stalks and the flowering stems all carry the same pungency as the rhizome in a milder, greener form, and picking them sensibly does the plant no harm. This is what makes the wait bearable, and it is the part most new growers do not realize they are allowed to do.
Pick outer leaves only, taking the stalk right down to the base with a clean cut, and never remove more than a third of the leaves on a plant at once. The center of the rosette must be left intact, because that is where all future growth comes from. Leaves regrow within a few weeks in cool conditions, so a mature plant can be picked from every two or three weeks through the growing season.
Flower stems appear in spring on established plants. Cut them out at the base when the buds are still tight and the stem snaps cleanly. They are crisp, and cutting them is what you want to do anyway if you are growing the rhizome on.
Judging when the rhizome is ready
A wasabi rhizome is the thickened vertical stem at the base of the plant, sitting just at and below soil level with the leaf stalks rising off it. It thickens slowly and steadily rather than swelling suddenly, so there is no dramatic sign that it is ready. The plant is telling you it has enough stored energy when the crown is thick and firm, the plant carries a full rosette of large leaves, and old leaf scars ring the stem from top to bottom.
Judge readiness by feel and by time rather than by a calendar date. Push the mulch aside and take the base of the crown between finger and thumb. At around eighteen months in good conditions, or two years in more marginal ones, a well-grown rhizome is roughly three quarters of an inch to an inch and a half (2 to 4 cm) thick and four to six inches (10 to 15 cm) long. Anything thinner than a finger is not worth lifting, and it will keep thickening if you leave it.
There is no advantage in leaving it far beyond that. Very old rhizomes go woody and hollow in the center, and plants that have flowered heavily for two seasons decline. If a plant is clearly stalling, shedding more leaves than it makes, or sitting in a site that has proved too warm, lift it and use it rather than gambling another season on it.
| Stage | Approximate age | What to pick |
|---|---|---|
| Establishment | First few months | Nothing. Let it build leaves |
| First season | 3-12 months | Outer leaves and stalks, up to a third at a time |
| Second spring | 12-18 months | Leaves, stalks and flower stems |
| Rhizome ready | 18-24 months | Whole plant lifted; rhizome, leaves and offsets |
| Overmature | Beyond 3 years | Rhizome may be woody or hollow; lift and divide |
Lifting the plant
Wasabi is harvested by lifting the entire plant, because the rhizome is the base of the stem itself. This ends that plant, which is why the offsets around the crown matter so much: they are next year's planting and they come out of the ground in the same operation.
- Choose a cool day Lift in cool, damp weather, ideally in autumn or early spring. Roots and offsets lifted in warm dry conditions dehydrate quickly and the replanted offsets are much slower to take.
- Loosen well outside the plant Push a fork in a hand's width from the crown on all sides and lever gently rather than digging close. The rhizome is brittle and snaps easily, and a broken rhizome does not store.
- Lift by the base, not the leaves Slide a hand under the root mass and lift the whole plant out together. Pulling on the leaf stalks tears them off the rhizome and takes a layer of the rhizome surface with them.
- Separate the offsets first Before cleaning anything, detach the side shoots with roots attached and put them straight into a bucket of cool water in the shade. Replant them the same day and you lose nothing from the bed.
- Trim and wash Cut the leaves off an inch (2.5 cm) above the top of the rhizome and trim the fine roots close. Wash under cool running water with a soft brush, working along the leaf scar rings where soil collects.
- Inspect the cut ends Firm, pale green flesh throughout is what you want. Brown streaking or a soft, hollow center means the plant was heat-stressed or waterlogged, and that part should be cut away.
Keeping what you lift
A cleaned rhizome keeps for around a month wrapped in a damp cloth in a sealed container in the refrigerator, and the cloth needs re-wetting every few days. It loses pungency steadily from the moment it is cut, so the flavor is at its best in the first week or two. Do not freeze a whole rhizome: it turns soft and watery when thawed.
Leaves and stalks keep only a few days, upright in a little water in the refrigerator like cut flowers. Pick them when you are going to use them rather than harvesting ahead.
Write down what you lifted: the date, the age of the plant from your planting note, the length and thickness of the rhizome, and how many offsets it gave you. Wasabi grown at home varies enormously with the site, and after two or three harvests that record is the only reliable way to know whether your bed is worth continuing with, needs more shade, or needs cooler water.