Growing Jerusalem Artichoke and Yacon: Two Tubers That Almost Grow Themselves

There is produce that worries you afresh every season, and then there is Jerusalem artichoke. Once you have the knobbly tubers in the garden, you harvest them for many years without ever planting again. Yacon is the slightly more demanding sister from the Andes: sweeter, juicier, but every winter a move into the cellar. Together the two make the perfect duo for anyone who fancies a potato alternative that is less prone to disease and brings fresh variety to the plate in autumn.

Two tubers, one principle: inulin instead of starch

Botanically, Jerusalem artichoke and yacon have more in common than their looks suggest. Both belong to the daisy family (Asteraceae), so they are more closely related to the sunflower than to the potato. And both store their reserves not as starch but as inulin, a soluble fibre. This makes the tubers low in calories, gives them their fine sweetness, and makes them interesting for people who watch their blood sugar.

The difference lies in temperament. Jerusalem artichoke is a long-distance runner that, once planted, is almost impossible to get out of the bed again. Yacon, by contrast, is a summer guest that does not survive the first frosty night and therefore moves outdoors anew every year. Anyone who knows both has fresh tubers to hand from October into March.

Jerusalem artichoke: the permanent guest that wants to stay

Jerusalem artichoke comes from North America and reached Europe as early as the 17th century, long before the potato caught on. The plant has an almost stubborn robustness: it grows on poor as well as good soil, tolerates drought, partial shade and deep frost. In late summer it forms bright yellow flower heads on stems two to three metres tall that look like small sunflowers and attract insects. As a screen or windbreak at the edge of the bed it makes itself useful along the way.

Beneath the soil sits the real treasure: light-brown to pink or purple tubers, knobbly and branched like ginger. Raw, they taste like a cross between artichoke and nut, slightly sweet, and they can be grated, fried, boiled or turned into soup. Because frost partly converts the inulin into fruit sugar, the tubers taste even more aromatic from November on. That is exactly why you are best off harvesting Jerusalem artichoke only after the first cold nights.

Yacon: the diva from the Andes

Yacon has been grown in the high valleys of the Andes for centuries and is still a genuine rarity here. The plant forms two quite different kinds of tuber: on top, right at the base of the stem, sits the knobbly rhizome crown with the sprouting buds. Below it hang the large, elongated storage tubers, which can grow from fist-sized to arm-length and make up the edible part. Only the crown serves for propagation; the storage tubers go into the kitchen.

Flavour-wise, yacon is a surprise: freshly harvested and cut open, the white, glassy flesh tastes juicy-sweet, a little like a mix of pear, watermelon and apple. Raw in a salad, cut into thin sticks as a snack or juiced is where yacon is best kept. The sweetness here too lies in the inulin and in fructooligosaccharides, which the body barely metabolises, which is why yacon is considered low in calories and gut-friendly.

The catch: yacon does not tolerate frost. Once the first cold night falls, the season outdoors is over, and you have to dig up the rootstock. In return, a single plant rewards you with several kilograms of tubers if it has had a long, warm summer.

Planting in spring

Both tubers go into the ground in spring, but at different times. Jerusalem artichoke is frost-hardy and may go out early; yacon has to wait until there is no longer any risk of a frosty night.

1. Choose the spot

   Both want full sun and loose, well-drained soil without waterlogging. For Jerusalem artichoke, pick a place where it is allowed to stay permanently, ideally at the edge of the bed or in a corner of its own.

2. Plant Jerusalem artichoke (CW 14 to 18)

   From late March to early May, set the tubers about 8 to 10 cm deep with 50 to 60 cm spacing. Work in some mature compost beforehand. Go easy on nitrogen, otherwise only the foliage runs riot.

3. Pre-sprout yacon (from February)

   In February or March, divide the overwintered rhizome crown into pieces with two strong buds each and grow them on bright and warm at about 18 to 20 degrees on the windowsill.

4. Plant out yacon (after the Ice Saints)

   Only after mid-May (CW 20), once there is no more risk of frost, do the young plants go outdoors with 80 to 100 cm spacing. Yacon needs room and a long summer.

5. Water and mulch

   Water regularly in dry spells, especially yacon during tuber formation from July. A layer of mulch keeps the soil moist and suppresses weeds.

Taming: keeping Jerusalem artichoke under control

The real issue with Jerusalem artichoke is not the growing but the stopping. Every tiny tuber left in the ground at harvest sprouts again in spring. If you are not careful, after three years you have a Jerusalem-artichoke thicket pushing into neighbouring beds. This is no cause for panic, but it is a reason to plan.

Another trick: do not plant Jerusalem artichoke right next to sensitive crops. As a bad neighbour it especially does not get on with the tomato. It harmonises well, on the other hand, with potato and onion. And if you find a variety that spreads less, go for it. There are cultivated forms with smoother, less branched tubers that are easier to harvest and behave a little more politely.

Harvesting and storing

Here the paths of the two tubers finally part. Jerusalem artichoke stays in the ground, yacon has to come out.

You harvest Jerusalem artichoke as needed from October into March. The tubers are best kept in the ground and keep better there than in any cellar, because they quickly go wrinkly after being dug up. So dig only as much as you need over the next few days. After the first frost, cut back the dead stems close to the ground.

Yacon, on the other hand, you dig up completely as soon as the first frost has turned the foliage black. Carefully separate the storage tubers from the rhizome crown. Lay the tubers in a sunny, airy spot for one to two weeks. This after-ripening converts inulin into fruit sugar and makes them noticeably sweeter. After that they keep cool and dark for many weeks. Bed the rhizome crown in slightly moist sand and store it frost-free at about 4 to 10 degrees in the cellar, where it waits for the next spring.

In the kitchen: ease in slowly

For all the enthusiasm about the sweetness, there is a practical note every newcomer should know. The inulin that makes both tubers so healthy is not digested in the small intestine but only broken down by bacteria in the large intestine. In unusually large portions this can cause considerable wind, which is why Jerusalem artichoke is jokingly blamed for flatulence in English.

The solution is simple: ease in with small amounts so your gut flora can adjust. Yacon is a little easier to tolerate here than Jerusalem artichoke. Cooking the tubers through also makes them more digestible. Raw in a salad, both unfold their fine, sweet aroma most beautifully; cooked, they become softer and milder. Try Jerusalem artichoke as a roasted vegetable with a little oil and rosemary or as a velvety soup, and yacon as a crunchy raw snack.