When to Harvest Sweet Potatoes: Days Frost plus Curing
When to harvest sweet potatoes depends on days from planting plus the weather. Clemson Cooperative Extension advises harvesting 90 to 120 days after planting, when about 30 percent of the roots are larger than 3½ inches across. Dig before frost, then start curing the roots before storage.
The short answer
Harvest sweet potatoes 90 to 120 days after planting plus before the first frost. Clemson Cooperative Extension advises digging when about 30 percent of roots exceed 3½ inches. WSU Extension notes there are no visible maturity signs, so dig a few plants to check. Start curing the roots warm before storing.
What are the harvest plus curing targets?
Extension services give clear numbers for digging plus curing.
| Stage | Target | Source |
|---|---|---|
| Harvest | 90 to 120 days after planting | Clemson Cooperative Extension |
| Root size | About 30 percent above 3½ inches | Clemson Cooperative Extension |
| Curing | 85F plus 90 percent humidity for one week | Clemson Cooperative Extension |
| Storage | 50 to 55F | Utah State University Extension |
| Shelf life | Over six months after curing | Clemson Cooperative Extension |
Sources: Clemson Cooperative Extension plus Utah State University Extension.
Why dig before frost plus cold soil?
WSU Extension advises harvesting before soil drops below 50F to avoid chilling injury. Utah State University Extension advises digging when foliage yellows or frost hits the vines, before the soil freezes. Clemson Cooperative Extension notes the skins damage easily, so dig gently with a fork.
How does curing work at home?
Clemson Cooperative Extension advises curing at 85F plus 90 percent humidity for one week, or in the warmest room of the house for about 14 days. No curing happens below 70F. Utah State University Extension notes curing for 1 to 2 weeks at about 80F works plus mends harvest wounds.
How to: step by step
- Track days from planting.
- Dig a few plants to check size.
- Harvest before frost plus cold soil.
- Lift roots gently.
- Hold roots warm plus humid for one to two weeks.
- Store at 50 to 55F.
Troubleshooting
Roots are small: dug too early. Dig closer to 120 days.
Roots rot in storage: stored too cold. Never store below 50F.
Skin peels off: fresh skins damage easily. Let skins set before storage.
For related reading see garden microclimates for cannabis, planning an outdoor cannabis garden layout plus fall garden cleanup after cannabis harvest. Kind Seed Co also stocks cannabis seeds.
Sources
- Sweetpotato, Clemson Cooperative Extension HGIC
- How to grow sweet potatoes in your garden, Utah State University Extension
- Growing sweetpotatoes in western Washington: production practices, WSU Extension
FAQ
Do sweet potatoes need curing?
Yes, for storage. Clemson Cooperative Extension advises curing at 85F plus 90 percent humidity for one week, or in a warm room for about 14 days, plus notes no curing happens below 70F. Curing mends wounds plus helps the roots store. Utah State University Extension advises 1 to 2 weeks at about 80F.
What happens if frost hits the vines?
Dig right away. Utah State University Extension advises harvesting when frost hits the vines plus before the soil freezes. Clemson Cooperative Extension advises harvesting before frost. WSU Extension notes soil below 50F can cause chilling injury, so a frost on the leaves is the signal to get the roots out.
How long do sweet potatoes last after curing?
Clemson Cooperative Extension notes sweet potatoes stored properly after curing can last more than six months. Utah State University Extension notes storage at 50 to 55F lasts 3 to 4 months. Clemson advises never storing them below 50F or in the refrigerator, since cold damages the roots.
How do I check if sweet potatoes are ready?
WSU Extension notes there are no visible signs of maturity, so dig a few plants to check root size. Clemson Cooperative Extension advises harvesting when about 30 percent of roots are larger than 3½ inches across. Utah State University Extension uses a thickness of 1½ to 2 inches as its guide.
What is chilling injury?
WSU Extension advises harvesting before the soil drops below 50F to avoid chilling injury, which damages the roots. Clemson Cooperative Extension advises never storing sweet potatoes below 50F or in the refrigerator for the same reason. Watch soil temperature in fall plus dig early if a cold snap is coming.
