There are so many good things about Jerusalem artichokes that in some ways it's surprising they're not grown more. They're tasty, available all winter, exceptionally easy to grow, completely undemanding, very low-maintenance and ideal for beginners. They are also low in calories. There's just one drawback, which I'll come to later.
The Jerusalem Artichoke (Helianthus tuberosus) is a perennial sunflower native to North America. It produces knobbly, white-fleshed (or, less commonly, red-fleshed) tubers that can be eaten raw or cooked. Better suited to cooler climates, they will grow in places like Florida, though your harvest is likely to be smaller.
It's often sold unnamed, and you could just buy some from your local grocery to plant out, but named varieties are becoming more common. In the States, French Mammoth White offers large yields. In the UK, Fuseau is popular because it's smoother-skinned than the others (in the US Golden Nugget and American are also smoother). It's also worth seeking out Dwarf Sunray. Being a bit more compact, with more flowers, it's better suited in the flower bed and its tubers don't require peeling.
Planting Jerusalem Artichokes
The tubers grow in just about any soil. This means that they're often relegated to a difficult area of the garden (ground that's waterlogged for extended periods is the only real no-no). That said, they will, like all vegetables, benefit from decent conditions. Improving poor soil before planting encourages the growth of larger tubers, which will be easier to cook later on. They prefer alkaline conditions, so add lime to raise the pH to around 6.5 if your soil is very acidic.
The sturdy, hollow stems grow tall enough to double as a living screen or windbreak, but unless you specifically want them for this purpose, don't plant too many. Five is probably ample. Remember, one tuber can produce twenty!
Plant tubers 4-6 inches (10-15 cms) deep, 12-18 inches (30-45 cms) apart. If they are already sprouting, make sure the shoots are pointing upwards, and be gentle, as they break off quite easily. If you don't have many tubers, you can cut them into pieces (don't let these dry out), ensuring that each piece has a bud on it, and plant those.
Caring for Jerusalem Artichokes
General advice is to keep them watered and earth up the stalks as they grow. There's no doubt you'll get a larger harvest, with larger tubers if you do. However, I'll admit that I neglect mine shamefully, even in dry spells, and never earth up, yet I still have more than I ever need.
Because they grow so tall (easily reaching ten feet or more), the plants can suffer wind-rock, or overshadow other crops. If this is likely to happen, cut stalks down to around 4 feet (120 cms) high in mid-summer. This will make them bush out and creates more compact plants. It also discourages flowering (which begins in autumn) and, instead, encourages them to put their energy into growing bigger tubers.
Their flowers provide some late nourishment for insects at a time when many flowers have long gone, though, so rather than cutting them back, you could corral them with deeply set canes and wires, so that they don't wave around over the bed.
Harvesting Jerusalem Artichokes
Start harvesting after the first frost, when the plants begin to die back (around late autumn—November in the northern hemisphere). If you're somewhere warmer then leave harvest until mid-winter.
Jerusalem Artichokes aren't easy to store well but one of their advantages is that they're quite happy left in the ground until you need them. If your ground tends to freeze, mulch well to ensure that you can extend the harvest period. If you do need to store them, ensure you put them somewhere very cool and with high humidity to help prevent them from shrivelling.
Replanting for the following harvest
It's not necessary to dig them all up if you've created a permanent bed for them, but they'll become congested in a couple of years if you don't. So, in early spring, dig over the bed, removing all you can find and replant (in the same place if you wish) the smoothest, biggest ones you come across. This helps ensure less knobbly artichokes in future years.
If you do get heartily sick of them, then covering the area with weed control fabric for a couple of years should see them off.
Eating Jerusalem Artichokes
The drawback to Jerusalem artichokes (and for some it's an insuperable problem) is that they contain inulin, a carbohydrate that feeds your gut bacteria. It's part of the reason why this vegetable is low in calories. It also causes wind.
I love them but can't eat too many at once. It's said that if you eat them everyday, the explosive effect wears off, but I've never actually come across anyone who's tried this and haven't had the courage to do it myself.
They do, however, make a delicious soup, either by themselves or in combination with carrots, sweet potatoes or even peppers. (To save my insides, I just make sure that they make up no more than 50% of the ingredients.)
The knobbliness of Jerusalem artichokes means that it's best to find ways to cook them that don't require careful peeling. Instead you can roast them in their skins or boil them for around twenty minutes until tender and then peel them.
They can also be eaten raw, grated into salads, when they're a bit like water-chestnut, but the flesh browns easily and, after peeling, tubers should be sprinkled with lemon juice or put into acidulated water until needed, to keep their whiteness.
By Helen Gazeley