Gadenin日本語Get the appThe first months: do almost nothing
From emergence to about knee height the plants need nothing but light. Hoe or hand-weed the row while you can still walk between the plants, because once the stems close over, weeds are shaded out permanently and you will not need to weed this bed again all year. This early window is the only weeding the crop ever asks for.
Do not thin the shoots. Each tuber usually sends up one to three stems, and the extra stems feed the tuber crop rather than competing with it. If a stem is snapped by wind, leave it; the plant compensates from the remaining ones.
Emergence is uneven, spread over two to six weeks depending on how cold the soil was at planting, so a gap in the row in mid spring is not proof that a tuber has failed. Wait until the rest of the row is a foot (30 cm) high before you dig one up to check, and resist filling gaps early; a tuber planted late into a row that has already closed over will be shaded out and produce nothing worth digging.
Feeding: less than you think
Jerusalem artichokes are the rare vegetable where generous feeding actively costs you yield. Nitrogen goes into stem and leaf, and by late summer you have ten feet (3 m) of top growth leaning over the path and a disappointing crop underneath. On any ground that has been cultivated at all, give nothing in the first year.
On genuinely poor or thin soil, a light dressing of a balanced fertilizer at planting is enough for the whole season. If you want to help the tuber phase specifically, a potassium-leaning feed in mid to late summer, at the point when flower buds appear, is the only supplementary feed worth giving. After that, feeding does nothing except delay dormancy.
| Soil | At planting | Midsummer | Late summer |
|---|---|---|---|
| Previously cropped garden soil | Nothing | Nothing | Nothing |
| Thin or poor soil | Light balanced feed | Nothing | Potassium feed if growth is weak |
| Recently manured bed | Nothing | Nothing | Nothing, expect tall tops and light crop |
| Container or raised bed | Light balanced feed | Half-strength liquid feed | Potassium feed once buds show |
A bed that grew a heavily manured crop the previous year still holds enough nitrogen to make sunchokes run to stem. Follow beans or brassicas with something else and give the sunchokes the hungrier ground.
Watering: one window that matters
For most of the year these plants find their own water. The root system goes deep and the leaves wilt visibly in heat and then recover overnight without any lasting harm, which fools people into watering when nothing was wrong.
The exception is the tuber-forming period, from the appearance of flower buds through to the point the leaves start to yellow, usually six to ten weeks. A dry spell in that window is the one thing that reliably reduces the crop, because tuber swelling stops and does not fully catch up afterwards. Water deeply, about an inch (25 mm) at a time, once a week during any dry spell in that period, and ignore the plants the rest of the year.
A mulch of straw or coarse compost along the row in early summer holds moisture through that window and saves most of the watering. It also keeps the surface tubers, which form shallowly on some plants, out of the light and stops them greening.
Cutting the tops down
When the leaves yellow and the stems start to dry, in mid to late autumn, cut the tops down to about twelve inches (30 cm) above the ground. Do not cut them earlier, however untidy they look, because the plant is still moving sugars down into the tubers right up until the foliage dies. Cutting green tops in late summer costs a noticeable share of the crop.
Leave the stubs standing rather than cutting flush. They mark exactly where each plant sits once the top growth is gone, which is what you need in winter when you are digging tubers a few at a time from frozen or muddy ground. The stems themselves are woody and slow to break down, so chop them before composting or use them as bean supports the following year.
Write down the date the leaves first yellowed. Compared year to year it tells you far more about how the season went than the harvest date does, because it marks the actual end of tuber growth.