Sweet Potatoes

Garden Help > Vegetables

The Basics

When to plant

Start slip production in February–March
Transplant to garden May–June

How to grow

Sweet potatoes are grown from 'slips' (sprouts from a sweet potato). Due to pest quarantines, most nursery companies cannot ship slips to California.
To grow your own slips:
- Start in February or March.
- Fill a shallow container that has drainage holes with moist potting soil.
- Nestle in the sweet potato so it is half covered in the soil. Place in a waterproof tray.
- Cover to retain humidity and keep it warm.
- Remove covering when sprouts appear in 2–4 weeks.
- When sprouts are 6 inches long, clip off 1 inch from potato (to prevent possible disease propagation from the mother potato) and plant directly in pots (or root in water then transplant into pots).

Care overview

Sweet potatoes grow best in light, loosened soils.
Do not over fertilize with nitrogen which encourages leafy growth at the expense of roots.
Wait to transplant until soil temperature reaches at least 70°F and night temperatures rarely dip below 50°F, typically May or June.
Plant rooted slips 12 to 18 inches apart. Do not crowd—plants need lots of room to develops large roots.
Once the vines spread to cover the ground, little weeding is required.
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.
Leaves and young shoots are edible and make a fine spinach substitute in the summer.

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

Harvest window

Sweet potatoes take 3–5 months to mature, so harvest in October–November. Leave in the ground until the roots are full grown and the vines begin to turn yellow.
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 (80–90°F, 85% relative humidity) for at least 10–14 days.
Placing a damp paper towel in paper bags of sweet potatoes is one way to create a humid environment.

Video

Growing Your Own Sweet Potatoes (3/11/2021) [1 hr 9 min]

More links

Sweet Potato Production in California

Recommended Varieties for Santa Clara County

There are no specific variety recommendations for Santa Clara County yet. The UC Davis Vegetable Research and Information Center's sweet potato overview lists some recommended varieties for California.