Saturday, 15 November 2014

Jerusalem artichoke (Helianthus tuberosus)

Jerusalem artichoke (Helianthus tuberosus) is also known as earth apple, sunchoke, sunroot, girasole and topinambour. From the Asteraceae family, this perennial plant looks very much like a sunflower and is grown for its sweet crunchy tubers. A native of North America, it was cultivated by native American indians long before Europeans settled in the region.

Jerusalem artichoke plants























  
Growing methods

Jerusalem artichokes are usually propagated vegetatively via tubers. Rhizomes, slips or cuttings can also be used. Easy to grow, Jerusalem artichokes will produce copious amounts of tubers. They only have to be planted once and they will continue producing tubers for many years to come. They can be grown in any soil or climate, and in full sun or partial shade. They probably do best in well dug fertile soil. Plant tubers at about 10cms in depth in the spring or the autumn in a permanent position.

To grow from seed, sow seeds in the spring under cover. Prick emerging seedlings out into individual pots and keep them undercover for their first year. Plant out into permanent positions the following spring or summer. Basal cuttings can be taken in the spring. Harvest shoots when they are 10-15cms long with plenty of underground stem. Pot them up and keep in light shade under cover until they root. Plant them out in the summer.

Jerusalem artichokes are tall plants so make sure they don't shade any other plants out. They can be mulched and watered and pretty much left to their own devices. They can also be mulched in the winter to stop the ground freezing in the winter and allowing easy harvesting. They are not frost tender.


Jerusalem artichoke tubers




















Tubers can be dug up at anytime but leave in the ground until required rather than lifting and storing. The tubers don't store well but if you have to place them in sand or peat to help retain the moisture. They have a thin skin which can easily be damaged allowing water to escape.Always leave a few in to continue the crop. The tops die down in the autumn and emerge again the spring. Cutting back the stems to just over 1m including the flowers helps to prevent the need for staking. We keep the flowers and stake where necessary as the flowers are very attractive. When foliage dies cut the stems down to about 8cm and leave on top as a mulch. Only water if really dry. It is recommended to replant in a different site every few years as the tubers will reduce in size. However, it really is up to the individual. There are now many named varieties to choose from.

Beware of slugs which may attack the young growth. Plants can be attacked by bacterial and fungal diseases later in the season or during storage. Sclerotina, a fungal disease, where plants rot at the base, may be a problem. To deal with this destroy infected plants. However, the disease may remain in the soil for a long time.

Raw edible parts

The white tubers have a crispy nutty flavour and can be eaten raw. They are often cooked in recipes and used in all the ways potatoes are used.

Other uses

Even if you don't eat the tubers, the flowers are stunning and the plant can be used as screening. Jerusalem artichoke can also be grown for biomass. The tubers are used in the production of inulin, ethanol and a sweetener. They can also be made into a coffee substitute. Jerusalem artichoke also has medicinal uses.

Issues

The inulin in Jerusalem artichokes can cause flatulence in some people. The amounts of inulin in the tubers varies. Inulin will depolymerize during storage, whether harvested or left in situ (Schorr-Galindo and Guiraud, 1997). Tubers, therefore, used late in the season, may be less of a problem for the digestive system. Another answer to the problem is to gradually increase the quantity of Jerusalem artichokes in the diet as the body does get used to the inulin over time.

Research on growing during the dry season in tropical regions showing that planting Jerusalem artichoke during lower temperature periods (10 -16°C) reduced total dry weight and inulin content, whereas inulin content increased when planted during warmer periods (21-31°C). AJCS 6(7):1159-1165(2012).

As a point of interest, chicory is also high in inulin.