They belong to the sunflower family, and are grown for their small knobbly underground tubers.
It is an easily grown plant, and can reach a height of 2-3 metres (7-10ft).
For this reason the bed should be kept away from other crops as the tall plants can overshadow and restrict growth of any nearby crops.
They are best grown in the same spot each year, so careful consideration should be given as to where to site them.
Keeping them in the one area can make it easier to control them.
For instance, if you miss a tuber when harvesting, it will grow like a volunteer potato.
This is no great problem if they remain in the same area, but can be a bit of a nuisance if they appear among another type of crop.
Some people grow them for the crop they give, and also to act as a windbreak.
They thrive in any ordinary, well-drained soil, in sun or partial shade.
No feeding or manuring is required as this will encourage the growth of foliage at the expense of tubers.
However it is advisable to prepare a new bed with plenty of manure in its first year.
Adding a mulch after the plants have been cut down each year should suffice for future crops.
Week 8: Plant the tubers* 400mm (15") apart and 125 mm (5") deep in rows 1 metre apart (39") (if ground conditions allow).
*Select small tubers, with at least one eye.
When they reach about 300mm (12") high, earth them up a little as you would potatoes.
Week 32: Give the plants a good soaking and apply an occasional liquid feed.
Removal of the growing tips along with flower buds will also help to direct the plant's energy into tuber production.
In exposed positions, support the plants, by stretching wires between posts at a height of about 2metres (6'6") to prevent stems rocking developing tubers out of the ground.
Lift the tubers when they have matured.
This is indicated when the top growth begins to turn brown.
The tubers may be lifted and stored in a clamp, but they keep their flavour and firm texture better if left in the ground until required.
If leaving them in the ground, cut the stems down to around 300mm (12") high to act as a marker.
Save a few small tubers for spring planting.