The yam is a vigorous climber. It can produce shoots up to 3m (10ft) long and these will need supporting. You can grow it like runner beans up a frame or bamboo canes.
Small tubers can be planted outside at the end of May after the fear of frost. For better and more reliable results the tubers are best planted up in pots of compost indoors and planted out at the end of spring when they have produced some growth.
Yams also form tubercles (small tubers) in late summer and early autumn in the leaf axils. These are a good way of propagating plants and make excellent planting material. Harvest them before they fall from the plant and store them in a cool, but frost-free place over the winter. Make sure they do not dry out. Pot them up into individual pots in early spring and plant them out when in actively growing in late spring or early summer.
Plants need a fertile well-drained soil. They prefer a position in full sun, although they will also succeed in light shade.
Yams produce long, vertical roots so it is possible to grow plants quite close together, spacing them 25-30cm (10-12in) apart.
Keep plants well watered and feed regularly with a balanced liquid fertiliser throughout the growing period.
Harvest the tubers in autumn, once the plants start to die down. Growing from tubercles produces smaller tubers, which are much easier to lift; those grown from tubers can need deep digging to harvest them.
lants that grow well with yams might be those that are also in the morning glory family, pest deterrents or simply those that complement the attractive foliage and starry purple flowers of sweet potatoes. When coming up with a crop planting scheme, don’t forget the importance of rotating crops. Many plant pests that are specific to a certain crop will overwinter in soil and refuse and rise like Lazarus in spring to plague your plants. Rotating helps reduce pest incidences by moving those insects’ favored foods and replacing them with something the pests don’t eat. One terrific species of plant that grows well with yams are any of the legumes. These plants actually enhance soil and crop growth because they harness nitrogen, a crucial nutrient for leafy growth and plant health. Pole type beans or peas are best because they can be trained to rise above the sweet potatoes. Companion planting with yams should also take into consideration the plot size and size of the plants. Yams will sprawl with vine-like growth, so using plants such as squash nearby is not advised.