Sweet Potatoes

Two orange sweet potatoes on a white background, one cut in half to show its bright orange flesh.

Sweet potatoes are the roots of a lush, green vine. They are grown from ‘slips’, the term for sprouts from a sweet potato. Due to pest quarantines, most nursery companies cannot ship slips to California. But they are easy to grow yourself.

Growing slips

In February or March, fill a shallow container that has drainage holes with moist potting soil.
Nestle the sweet potato into the soil so it is half covered. Place in a waterproof tray.
Cover to retain humidity and keep it warm.
Remove covering when sprouts appear in 2 to 4 weeks.
Alternatively, use toothpicks to suspend the sweet potato half-submerged in a jar of water in a warm location. Change the water occasionally. Soon sprouts will appear.
When sprouts are about 6 inches long, clip them off 1 inch from the potato to prevent possible disease propagation from the mother potato. Plant into pots or root in water then transplant into pots.

Two sweet potato slips: one in a dark green pot with soil and leaves, and another in a clear jar filled with water, showing roots.

Planting

Transplant rooted slips to garden 12 to 18 inches apart in May to June.
Wait to transplant until soil temperature reaches at least 70°F and night temperatures rarely dip below 50°F.
Sweet potatoes grow best in light, loosened soils.
Do not over fertilize with nitrogen which encourages leafy growth at the expense of roots.
Do not crowd. Plants need lots of room to develop large roots.
Once the vines spread to cover the ground, little weeding is required.

Harvesting

Sweet potatoes take 3 to 5 months to mature, so harvest in October to November. Leave in the ground until the roots are full grown and the vines begin to turn yellow.
Leaves and young shoots are edible and make a fine spinach substitute in the summer.
For best harvests, prevent vines from rooting along the stems by mulching the soil, lifting the vines off the soil periodically, or trellising the vines.
Stop watering 2 weeks before harvesting.
Dig carefully to prevent skinning and bruising. Do not wash immediately because the skins are very tender. Allow newly harvested sweet potatoes to dry in the garden for a few hours.

Curing

A cluster of freshly harvested sweet potatoes in various shapes and colors, resting on dark soil, with lush greenery in the background.

Curing improves flavor by converting starches to sugars, helps minor scrapes heal over, and increases storage time.
To cure sweet potatoes, store them in a warm, humid place (80 to 90°F, 85% relative humidity) for at least 10 to 14 days.
Placing a damp paper towel in paper bags of sweet potatoes is one way to create a humid environment.

Pest management

Sweet potato diseases, Texas A&M Plant Disease Handbook
Sweet Potato & Irish Potato Insects, Clemson Cooperative Extension
Sweet potatoes share some pests with potatoes, UC IPM

Recommended varieties for Santa Clara County

There are no specific variety recommendations for Santa Clara County yet.