Growing Sweetpotatoes

Sweetpotatoes succeed best in the southern U.S., but they are grown in home gardens as far north as southern Ontario. They can be grown even farther north, in sections having especially mild climates, such as British Columbia. In general, sweetpotatoes may be grown wherever there is a frost-free period of about 150 days with relatively high temperature.

The young leaves and shoots are sometimes eaten as greens. The sweet potato is only distantly related to the potato (Solanum tuberosum). Although the sweet potato is sometimes (incorrectly) known as yam in the United States, it is unrelated to the botanical yam.

A well-drained, moderately deep sandy loam of medium fertility is best for sweetpotatoes. Heavy clays and very deep loose-texture soils encourage the formation of long stringy roots. For best results the soil should be moderately fertilized throughout. If applied under the rows, the fertilizer should be well mixed with the soil.

In most of the area over which sweetpotatoes are grown it is necessary to start the plants in a hotbed, because the season is too short to produce a good crop after the weather warms enough to start plants outdoors.

Bed roots used for seed close together in a hotbed and cover them with about 2 inches (5cm) of sand or fine soil, such as leafmold. It is not safe to set the plants in the open ground until the soil is warm and the weather settled. Toward the last, ventilate the hotbed freely to harden the plants.

The plants are usually set on top of ridges, 3 1/2 to 4 feet  (1.1 to 1.2m) apart, with the plants about 12 inches (30cm) apart in the row. When the vines have covered the ground, no further cultivation is necessary, but some additional hand weeding may be required. Because the vines of spreading varieties need a great deal of space, allow at least 3 to 4 feet (1 m)between rows.

Dig sweetpotatoes a short time before frost, on a bright, drying day when the soil is not too wet to work easily. On a small scale they may be dug with a spading fork, great care being taken not to bruise or injure the roots. Do not water during the last 3 to 4 weeks before harvest to protect the developing roots.

Let the roots lie exposed for 2 or 3 hours to dry thoroughly but not in direct sunlight during the hot part of the day; then put them in containers and place them in a warm room to cure. The proper curing temperature is 85F (30C). Curing for about 10 days is followed by storage at 55 degrees to 60 degrees (10 to 15C).

Sweet potatoes should be handled as little as possible to avoid scuffing and bruising. In case of frost, cut the vines from the roots immediately to prevent decay spreading from the vines to the roots and dig sweet potatoes as soon as possible.

Cold soil temperatures quickly lessen the roots’ ability to keep in storage. Do not allow roots drying in the garden to be frosted because they are quickly ruined. For best quality, use the potatoes as soon as possible after they have been stored.