How to Grow Sweet Potatoes

Flowers are large and white, like their related cousin 'Morning Glory', and the tubers come in various colours and sizes, formed as the food reserve of the plant.

For successful growing plants need a warm frost free location in full sun.

In temperate climates it is best to plant in October to November similar to growing tomatoes, and harvest in late autumn. In the sub tropics and tropics they can be grown year.

Tubers are best planted in a warm sheltered position with a greater than 20°C soil temperature. In cooler climates they are best started using two methods.

Tubers in pots: Plant tubers whole into good quality potting mix, in a large black pot, at a depth of 7cm in late spring. Shoots should appear within a few weeks at which time you can then plant into the garden (see planting instructions below).

Struck cuttings: Cut tubers into two and place the fat end on moist cotton wool. Place in a warm sunny position such as a window sill. Once plants begin to shoot they can be planted following the below instructions.

Planting into garden instructions: Sweet potatoes need an organic rich well drained soil. Plant 10 cm deep or so the shoot tip is just above the soil surface. Space at 50 cm intervals and 1 metre between rows.

Once plants have begun to grow you can 'hill up' soil by adding more a mix of compost and manure but ensuring the stems and tips are still visible. Repeat this process during the growing season to encourage the formation of extra tubers. You can also hill plants vertically along the ground.

If limited for space plants can be grown up tee pees in a 1 square metre area, or allow plants to grow naturally along the ground to a spread of 1.5 metres plus.

Crop rotation should occur every 12 months to help prevent disease and nematode build up.

Plants require a long growing season of greater than 240 days plus before you would expect to be able to harvest. Harvesting usually takes place when plants begin to go dormant (leaves begin to deteriorate) in late autumn / winter.

After 240 plus days you can gently check for tubers by digging down using your hands. If plants are still actively growing you can ‘bandicoot’ out the largest tubers and leave the smallest to mature later.

In cooler climates you may find that plants produce multiple smaller sized tubers which will need to be harvest before winter.

Place tubers out of direct sunlight and allow them to dry before storing. Stored tubers should last 6 to 9 months if growing 'Beauregard' and 2 to 4 months for other cultivars like 'Hawaiian Sunshine'