Sweet potato is a great crop to grow in warm to hot areas, where it can often be difficult to grow traditional potatoes. It’s a very hardy crop and one of the easiest to grow, and it provides excellent returns of big golden or purple tubers. You can also eat the leaf tips and young leaves as spinach.
By Phil Dudman
At a glance
Ease of culture: Easy
Where: All zones except cold
Best climate: Warm to hot conditions
When: Spring, summer
Spacing: 40cm
Harvest: 4 months
pH: 5.5-6.5
Climate
• Sweet potato likes warm to hot conditions
• Grows best in tropical and subtropical areas where it can be planted year round
• Will produce good crops in temperate areas, but will need at least 4-6 months of warm frost-free conditions to produce a good crop, so plant early spring
Position
• Best crops are produced in open sunny positions with full-day sun, but you can also get a reasonable return in half-day sun and semi-shaded positions
Soil
• Sweet potato needs a deep, loose friable and well-drained soil to allow tubers to develop and avoid rotting in times of heavy rainfall
• Dig over the soil to at least a spade’s depth and incorporate a minimum of 2 bucketloads of compost or well-rotted manure per square metre. Mound the soil into deep planting ridges 40cm wide, to create greater depth and improved drainage
• In heavy soils and heavy rainfall areas, build an even greater depth of soil by mounding rows of garden waste and soil on the soil surface
Planting
• Sweet potato is a perennial vine that covers the ground
• The plants are propagated using cuttings
• Start by planting a healthy sweet potato in the ground or in a pot filled with potting mix when the weather is warm
• Keep it watered and it will start producing shoots which can be used as cutting material
• Take cuttings 15-20cm long, remove all leaves except two at the top, and plant them directly into the soil with the top leaves just above the soil surface
• Keep the soil moist and they will start forming roots within a week. New tubers will form from these roots. The tops will produce lots of green shoots which can also be used as cuttings
• Continue to plant more cuttings as material becomes available
Watering, fertilising and maintenance
• Keep plants evenly moist, but not too wet. Water deeply during dry periods
• Sweet potato needs a good supply of potassium and phosphorous for tuber production. The simplest way to supply this is with compost and an application of a well-balanced organic fertiliser once every 8 weeks during the growing period
• This is a vigorous and often rampant plant during the peak growing time. Trim growth as it escapes using pruning shears or a sharp spade. The prunings can be used as cuttings for new plants or added to the compost heap
• The vines will form roots and potential tubers wherever the nodes (leaf joints) make contact with the ground. This can be further encouraged where appropriate by building soil and compost up around trailing vines
Harvesting and storage
• Tubers are ready for harvest in 4 months from planting in tropical areas and 6 months in cooler zones
• To harvest, pull back vines to reveal their base and then use a garden fork to loosen the surrounding soil and expose the tubers. There can be several tubers ready at each planting spot
• In warm areas, plants can be left in the ground for several years
• In cooler areas, harvest crop before winter
• Large tubers store best. Wash and air-dry for a few days and store in the fridge
Pests and disease
Sweet potato is a very hardy crop that is generally free from pest and disease problems
In the kitchen
Sweet potatoes are delicious baked, boiled, steamed or fried. Add it to curries and casseroles 10 minutes before serving, or use it as a substitute for pumpkin in cakes and pies. Exposed flesh discolours quickly – to avoid this, add it to water soon after peeling and chopping. The young leaves and shoots are also edible and can be used in salads, either steamed or stir-fried.
Varieties
There are two main varieties of sweet potato readily available in Australia. The orange-flesh variety is most common and is sweet and moist. The purple-skinned variety with white flesh has a richer flavour but slightly dryer texture.
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