Jerusalem artichoke

How to recognise it

Habit

Perennial of 1.5–3 m with straight stems branched near the top; forms dense stands through tubers and underground runners.

Leaf

Oval to lance-shaped, 10–25 cm, toothed, rough as sandpaper, with three main veins and a winged stalk; opposite below, alternate above.

Flower

Golden yellow heads of 4–8 cm with 10–20 ray florets and a yellow centre, from late August into October.

Fruit/Seed

Rarely sets ripe seed here; it spreads mainly by its tubers.

Roots

Underground runners with knobbly tubers of 5–10 cm, with white, yellow, red or purplish skin.

Look-alikes

The sunflower is annual, has no tubers and has a large brown centre. Other perennial sunflowers and coneflowers (with a dark centre) have no edible tubers; if in doubt, scrape away the soil to look for tubers.

Flowering: August–October · Pruning: March and November

Why grow it?

• An easy, hardy vegetable: the tubers stay in the ground and you dig them as you need them, from November to March.
• Late flowers in September–October, with nectar and pollen for bumblebees, bees, hoverflies and butterflies when little else is in bloom.
• A fast, tall summer screen or windbreak at the edge of the vegetable plot.
• Its dense stems give shelter to birds and insects in late summer.
• A nutty flavour, grated raw or cooked in soup, mash or roasted.

Jerusalem artichoke: where does it grow best?

• In the wild along riverbanks, on waste ground, rough verges and old garden land.
• Sun to light partial shade; in sun it gives the most tubers and flowers.
• Almost any soil, ideally loose, moisture-retentive sand or loam; on heavy clay the tubers stay smaller and are hard to lift.
• Choose a permanent spot at the edge of the vegetable plot, where its shade does not bother other crops and it cannot spread between them.
• Never beside a stream or river or near nature reserves: pieces of tuber wash downstream and grow into dense stands that crowd out other plants.

Goes well with

• Hemp-agrimony: Also flowers late in the year and attracts many butterflies, in a wild strip beside the bed.
• Tansy: Yellow buttons in late summer, for hoverflies and small beetles.
• Purple loosestrife: Purple spikes on moist soil that complement the yellow flowers nicely.
• Pot marigold: An annual for the edge of the bed, flowering until the frosts for bees and hoverflies.

Jerusalem artichoke: when and how to plant it?

1. Buy seed tubers from a garden centre or seed merchant, or use healthy tubers from your own harvest; never dig up plants from the wild.
2. Plant in March–April, as soon as the soil can be worked, 10–15 cm deep.
3. Leave 40–50 cm between tubers and 75–100 cm between rows.
4. Plant them in a separate bed or put a root barrier 40–50 cm deep around the bed so they do not spread.
5. Water during dry spells until the shoots are above ground; after that only in dry summers.

Care

Watering

In dry summers water generously in August–September: that is when the tubers grow fastest.

Feeding

Not needed on rich soil. On poor sandy soil, a layer of compost in spring.

Earthing up

In June, earth up the stems by 15–20 cm: they stand more firmly and you get more tubers.

Spreading

Every piece of tuber regrows. Harvest thoroughly every year, including the small tubers, or keep it within a root barrier.

Harvesting

From November to March, as much as you need each time. Tubers keep best in the ground; lifted tubers keep cool in damp sand.

Tip: At every harvest, lift even the smallest tubers and keep a few good ones aside to replant in March: the bed stays tidy and you know exactly where the Jerusalem artichokes will be next year.

Pruning and mowing

Pruning months: March and November.

When: In November, after the first frost, and the last stems in March.

How:

• After the first frost, cut the dead stems back to 20–30 cm above the ground: this shows you where to dig.
• Leave a few stems at the edge until March as shelter for insects, then clear them.
• Compost the stems, but never tubers or pieces of tuber: they will sprout again.
• If it grows too tall or blows over in summer, you can top the stems at 1.5–2 m in July.

Caution: Never dump tubers or root remains in the countryside, in a stream or on a cold compost heap: they regrow everywhere. Waste with tubers belongs in the green waste collection.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Tubers

In March–April, plant a healthy tuber or a piece with at least one eye. Each tuber gives a new plant with a whole cluster of new tubers.

Seed

Rarely sets ripe seed here, so it is propagated almost only from tubers.

Jerusalem artichoke: how does it get through the winter?

Hardy to −30 °C.

• The stems die at the first frost; the tubers overwinter in the ground and tolerate hard frost.
• In hard frost the soil is hard to dig: lay straw or leaves over the bed in November, or lift a supply in advance.
• After some frost the tubers often taste sweeter.
• Leave a few dead stems standing: insects overwinter in them.

Diseases and pests

• Spreading: Small tubers left behind sprout again every year, even between other vegetables. Harvest thoroughly, use a root barrier and pull up new shoots straight away in spring.
• Mice and voles: They gnaw the tubers in the ground. Lift some in autumn and store them in damp sand in a mouse-proof place.
• Blowing over: The tall stems blow over in storms. Earthing up, a sheltered spot or topping in July helps.
• Powdery mildew: White powder on the leaves in late summer. Harmless for the harvest; give space and water during drought.
• Slugs: They eat young shoots in April–May. Collect them in the evening and attract hedgehogs and ground beetles with a wild corner.

Through the year

• January: Harvest in mild weather.
• February: Harvest. Lift the last tubers before they sprout.
• March: Plant. Clear the last dead stems.
• April: Plant. The first shoots appear; watch out for slugs.
• June: Earth up. Weed out tubers sprouting outside the bed.
• August: Water during drought. First flowers.
• September: Flowering: bumblebees, bees and butterflies.
• October: Last flowers. The tubers are still growing.
• November: Cut back stems after frost. Harvest begins. Straw over the bed.
• December: Harvest as needed.

Did you know?

• The French name topinambour refers to the Tupinambá, a people from Brazil who became known in France around 1613, even though the plant comes from North America.
• The English name ‘Jerusalem artichoke’ has nothing to do with Jerusalem; it is often explained as a corruption of the Italian girasole, ‘sunflower’.
• Helianthus means ‘sunflower’, from the Greek helios, ‘sun’, and anthos, ‘flower’: the Jerusalem artichoke is a close relative of the common sunflower.