Name: sweet potato, sweet potato vine, kumara (Ipomoea batatas).
Plant type: perennial, but generally grown as an annual.
Foliage: broad, heart-shaped or lobed leaves.
Climate: cool and warm temperate zones, sub-tropical, tropical.
Soil: moist, well-drained and enriched with plenty of organic matter.
Position: full sun.
Flowering: white trumpet-like flowers with a magenta-coloured centre.
Feeding: feed regularly throughout the season.
Watering: water regularly to keep soil moist.
Despite the name, sweet potatoes are not related to the common potato. However, they do produce delicious sweet and starchy tubers that can be enjoyed in the same way as potatoes. They grow into a sprawling vine that will happily spread and put down roots if given the space. Sweet potato leaves can vary in shape and colour, but are generally green and heart-shaped or lobed. They are also edible and can be consumed raw or cooked.
The underground tubers – the best part of the plant – can be orange, but sweet potatoes are available in other colours, too, including red- or white-skinned varieties with white flesh, or white-skinned with purple flesh (WSPF).
Use sweet potatoes in any recipe that calls for potatoes – they’re the perfect substitute. Enjoy them baked, roasted, mashed or steamed. For a fun project, you can also grow sweet potatoes as an ‘indoor plant’. Put a sweet potato in a jar or glass with the pointed end facing down, and fill with enough water to cover the bottom half of the tuber – use toothpicks to help hold it in place if necessary. Place it in a warm, brightly lit spot and change the water weekly. Shoots and leaves should form after a few weeks.
In cool and warm temperate zones, the best time to plant is in spring, after the last frost. In subtropical and tropical climates, sweet potatoes can be planted year-round. Choose a sunny spot with well-drained soil. Enrich with plenty of compost and aged manure and fork in well. Plants can either be grown from cuttings or rooted sprouts, aka ‘slips’. You can plant a whole tuber, but it will take longer to establish.
You can buy slips or grow your own by placing a sweet potato in a tray filled with potting mix. Half bury the tuber in the mix and mist or water regularly to keep the soil moist. Sprouts will grow and root over the next couple of weeks. Once they’re about 12–15cm long, they can be separated from the tuber and used for planting. Alternatively, take cuttings from mature plants, remove most of the leaves and insert into the prepared soil.
Plant slips or cuttings 40–60cm apart and water regularly until established.
Sweet potatoes are fairly hardy once established. They will root at nodes that come into contact with the soil, which in turn will help more tubers develop. Regularly bury nodes to encourage a bumper crop, but don’t worry if you can’t be bothered – the plant will still grow well.
Water regularly after planting to keep the soil moist. Water sparingly once established, but increase frequency during dry periods.
Apply an organic pelletised fertiliser once every 6–8 weeks.
Sweet potatoes are ready for harvest when the vines and foliage die back. This is usually 16-18 weeks from planting, but can be longer in cooler climates. Carefully loosen the soil using a garden fork, then dig for the tubers with your hands or a small fork. Take care not to damage the skin of the tubers as this can impact storage. Use a dry brush to remove most of the dirt before storing in a cool, dry place.
If growing in tropical climates, tubers can be left in the ground where they can continue to live and produce for years. In other climates, lift all tubers before winter.
Sweet potatoes are generally pest- and disease-free. Grasshoppers may occasionally feed on the leaves, but they don’t usually pose a threat to the plants.
Sweet potatoes can be easily grown from cuttings or slips.
After applying fertiliser, delay harvesting for a few days and rinse well before cooking and eating. If using products to deal with pests, diseases or weeds, always read the label, follow the instructions carefully and wear suitable protective equipment. Store all garden chemicals out of the reach of children and pets.
Fennel: this bulbous stem has a wonderfully subtle aniseed flavour; perfect raw or cooked.
Parsnip: a hearty winter vegie with a sweet, earthy flavour.
Horseradish: a spicy root vegie that is often used as wasabi substitute.
Check out our huge range of plants now and get your garden growing!