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Jerusalem artichokes are planted from tubers, and every tuber fragment left in the soil at harvest becomes a plant the following season. A piece the size of a thumbnail is enough. This is not a failure of technique; it is how the plant works, and no amount of careful digging changes it. Treat the first planting as a permanent decision and you will avoid the argument you would otherwise have with this crop for the next five years.
That means putting them somewhere you are happy to keep growing them: the far end of the plot, a strip along a fence, a corner that nothing else wants. Do not put them in the middle of a rotation bed. Do not put them where you plan to grow anything low the year after. The stems reach six to ten feet (1.8 to 3 m) and cast a hard shadow, so anything on the north side of them in the northern hemisphere, or the south side in the southern hemisphere, will be shaded from midsummer onwards.
The upside of that permanence is that the crop asks almost nothing of you. Poor soil, thin soil, a windy corner, ground too rough for carrots: sunchokes will produce a usable crop in all of it. Rich, heavily manured soil gives you tall lush stems and a surprisingly ordinary crop of tubers, so save the compost for something that repays it.
If you have any doubt about giving up the ground, plant into a bottomless container or a raised bed lined on the sides, sunk into the soil, so the runners hit a wall. It does not stop them completely but it turns a spreading colony into a manageable one.
When to plant
Plant in early spring, as soon as the soil can be worked and is no longer waterlogged, at around 45 to 50F (7 to 10C). They are far tougher than potatoes and the emerging shoots tolerate light frost, so there is no reason to wait for settled warmth. Tubers planted while the ground is still cold simply sit and wait, which does them no harm.
Autumn planting works too, in mild areas, and matches what the plant does on its own: tubers left in the ground overwinter perfectly well and sprout when they are ready. The trade-off is that you lose track of exactly where they are and you cannot correct the spacing. If you do plant in autumn, mark the row with canes so you know which shoots in spring are the crop and which are strays.
| Timing | Soil condition | What you get |
|---|---|---|
| Early spring | Workable, above 45F (7C) | Even emergence, spacing under your control |
| Mid spring | Warming, drying | Slightly later start, no yield penalty |
| Autumn, mild winters | Still warm from summer | Earliest emergence, spacing drifts |
| Late spring or summer | Warm and dry | Short stems, small tubers, poor crop |
Depth, spacing and the size of the seed piece
Use tubers about the size of a hen's egg, roughly two ounces (50 to 60 g). Larger ones can be cut, as long as each piece carries at least two visible buds, but unlike potatoes there is little advantage in cutting and the cut faces are more prone to rot in cold wet ground. Whole tubers are the simpler choice.
Plant four to six inches (10 to 15 cm) deep with the buds facing up, spaced twelve to eighteen inches (30 to 45 cm) apart in rows about three feet (90 cm) apart. Closer spacing gives you more stems and smaller tubers; wider spacing gives fewer, larger, easier to clean tubers. Since cleaning knobbly tubers is the single worst job this crop asks of you, err towards the wider end.
- Loosen the row, not the whole bed Fork the planting row to a spade's depth so the tubers can swell downward. There is no need to dig or manure the whole bed. On heavy clay, a shallow ridge along the row helps the ground drain and warm.
- Set the tubers Buds uppermost, four to six inches (10 to 15 cm) deep. On very light sandy soil go to the deeper end so the plants anchor better against wind later in the season.
- Cover and firm Backfill and firm gently with the back of a rake. Do not water in unless the soil is dust dry; cold wet soil around a dormant tuber is the one condition that rots them.
- Mark the ends of the row Push a cane in at each end. Emergence takes two to six weeks depending on soil temperature, and in that gap it is easy to hoe the row by mistake or plant something else on top of it.
What to write down at planting
Keep a record of the planting date, the exact position of the row, the spacing you used and the weight of tubers you put in. The last one matters more than it sounds: sunchoke yields are usually quoted as a multiple of what was planted, and without the starting weight you have no way of judging whether a heavy-looking harvest was actually good.
Also note where the row edges are relative to a fixed thing, such as a fence post or a path corner. Next spring the colony will have moved, and the only way to know whether it has crept two feet or ten is to have written down where it started.