Growing a lovely houseplant from a common sweet potato straight from the grocery cart is just as much fun for kids today as it was in Grandma's time. If you help your children sprout one, you can share in their delight as purplish-green leaves emerge from the top of a vegetable you usually boil and mash, or candy in butter and brown sugar. And, if you're lucky, your child's plant may produce some lilac-coloured blossoms.
The stubby vegetable is actually the storage root of Ipomoea batatas—the botanical name for the white or yellow sweet potato and the orange yam. Sweet potatoes are tropical American members of the morning glory family. Outside, they grow best where summers are fairly long and warm. Inside, they were once common houseplants grown on kitchen windowsills, the beautiful vines trained up and around window frames.
To help your kids grow their own vine, choose a firm sweet potato. Some are treated with heat to keep them from sprouting on grocery-store shelves, but most grow roots in a matter of days after being placed in water. Using four toothpicks, have your child suspend the vegetable on the rim of a jar or mug filled with water. Make sure the bottom half—the pointed end—is under water. Place in a sunny spot, and change or add water as needed. In a few days, roots will form below the water. And, two to three weeks later, leaves and stems will sprout from the top. Continue to grow the plant in water or, after a month or two, pot the sweet potato in a houseplant potting mix. Keep the soil moist. The stems are weak, so help your child tie them to strings, wire or a stake. Feed once a month with a balanced water-soluble fertilizer such as 20-20-20. As the vine grows, cut it back a few inches to force the plant to grow bushy.
If your kids want to try growing sweet potatoes in your garden, you can have them root 25- to 30-centimetre (10- to 12-inch) cuttings in water, then plant them outside in late May to produce sweet potatoes they can dig and eat in the fall. Plant 30 centimetres (one foot) apart and feed once a month with 5-10-10 fertilizer. Mulch with straw or dry leaves to control weeds, and keep the soil moist. The tubers need approximately 120 days to mature, so let them grow as long as you can. But don't let frost hit them. In case of an early frost, cover the plant overnight with newspaper to keep the vines growing. Late in the season, probe beneath the vines to test the size of the tubers. Be careful not to puncture or bruise them. Store the tubers in a cool, dry place, and wrap them in newspaper to keep them from sprouting.
Some varieties of sweet potato vines are so attractive, they're sold as ornamental foliage plants at garden centres. They're striking in window boxes and containers, and also make great groundcovers. Some even produce edible tubers. Pinched-off tips can be rooted in water and the tubers can be saved till late winter or early spring to sprout in water just like their grocery-store cousins.
- Ipomoea batatas 'Blacky': Dramatic dark purple foliage with large lobed leaves
- Ipomoea batatas 'Marguarita': Heart-shaped, chartreuse foliage
- Ipomoea batatas 'Tricolor': Striking pink, white, and green leaves