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.
- 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.
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
- 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
More links
- Video: Growing Your Own Sweet Potatoes (3/11/2021) [1 hr 9 min]
- Video: Sweet Potato Slips (2/19/25) [2:36]
- Sweet Potato Production in California
Recommended varieties for Santa Clara County
There are no specific variety recommendations for Santa Clara County yet.