How to grow sweet potato
Family Convolvulaceae. Hardy to USDA hardiness zone 3a+ (U.S. Department of Agriculture). Full sun, 8+ hrs. Ready in 90-120 days.
Sun
Full sun, 8+ hrs
Spacing
12-18 in, rows 36 in
Days to harvest
90-120 days
Hardiness
Zone 3a+
What growers actually recorded
Loading zone 7b results…
When to plant sweet potato
- Transplant out: ~3 weeks after last frost.
Companion plants for sweet potato
Plant with: Bush bean, Radish, Marigold, Thyme.
Avoid near: Squash, Pumpkin.
Common pests & problems
Sweet potato weevil, wireworm, deer browsing on vines.
Feeding & fertilizer
N-P-K ratio: Low N, higher K (5-10-10)
Organic options: Compost worked in before planting slips · Wood ash or kelp meal for potassium · Skip nitrogen once vines run
When to feed: One feed at planting, one potassium boost 6 weeks in. Nothing after that.
Watch for: Lush vines and no roots = too much nitrogen. Sweet potatoes want lean soil.
N = nitrogen (leaves), P = phosphorus (roots and flowers), K = potassium (fruit and disease resistance). How to read a fertilizer label →
Grower's tip
Plant rooted slips, not seed. Wait until soil holds 65F, then let vines sprawl and cure roots at 80F for 10 days before storage: that curing step is what makes them sweet.
When to plant sweet potato in your zone
Free month-by-month sowing and transplanting lists, built from frost dates for your USDA (United States Department of Agriculture) hardiness zone.
Soil & water for sweet potato
Soil & pH
5.8-6.2: slightly acidic
Loose, sandy loam with excellent drainage; heavy clay produces misshapen, forked roots.
Build a raised ridge or hill 8-10 in tall to warm the soil and give roots room to swell. Avoid fresh manure or high-nitrogen feeding, which pushes vine growth over root formation.
Watering
1 in / week; taper sharply in the final 3-4 weeks before harvest
Deep, infrequent watering at the base; sweet potato vines tolerate heat and some drought well once established.
Reducing water in the weeks before harvest concentrates sugars and toughens skin for better storage; don't chase the vines with extra irrigation late in the season.
Knowing when to harvest
- Dig a test root once vines start yellowing, or 90-120 days after planting slips, whichever comes first.
- Harvest before the first frost touches the vines; cold-damaged roots store poorly and rot quickly.
- This crop is grown from rooted vine cuttings called slips, not seed potatoes; there is no 'seed piece' stage like a true potato.
Storing & keeping
Cure immediately at 80-85°F, 85-90% humidity for 5-7 days; this step is essential and converts starch to sugar while healing skin wounds. After curing, store at 55-60°F, 80-85% humidity for 4-6 months. Never refrigerate: cold below 50°F causes chilling injury and an off, hard core.
What to expect
Per plant: 2-5 lb of roots per slip planted
Troubleshooting sweet potato
Roots are small, stringy, or oddly forked
Likely cause: Compacted or heavy clay soil, or too much nitrogen pushing vine growth
What to do: Grow in raised, loosened ridges; go easy on nitrogen and let the soil stay on the lean side.
Roots rot within weeks in storage
Likely cause: Skipped curing, or storage temperature too cold or too damp
What to do: Always cure fresh-dug roots at high heat and humidity before moving to cooler long-term storage.
Confusion about calling this a 'potato'
Likely cause: Sweet potato (Ipomoea batatas, a morning glory relative) is unrelated botanically to the true potato (Solanum tuberosum, a nightshade)
What to do: Treat their culture as entirely separate: different family, different pest and disease profile, different propagation method (slips, not seed pieces).
Varieties worth the space
Not every name in a seed catalog. These are the ones growers order again, with what each one is actually good at and what it asks of you.
Beauregard
Open-pollinated · 100 days
The commercial orange standard; fast enough for northern gardens with black plastic.
Georgia Jet
Open-pollinated · 90 days
Earliest of the common slips, the pick for a short season.
Murasaki
Open-pollinated · 110 days
Purple skin, white flesh, drier and nuttier than orange types.
Japanese Purple (Murasaki)
Purple skin, ivory flesh, firmer texture prized for roasting.
Growing sweet potato in containers
15-20 gallon grow bag works well; sweet potato vines sprawl widely but the roots themselves develop fine in a deep, loose container.
Nutrition
A meaningful source of vitamins, minerals, and fiber when eaten fresh.
Common questions
Is a sweet potato actually a potato?
No, despite the name they are unrelated: sweet potato is in the morning glory family and grows from rooted slips, while true potato is a nightshade grown from seed pieces.
Why does curing matter so much?
Curing at high heat and humidity converts starch to sugar and heals skin cuts from digging; skipping it results in bland flavor and roots that rot quickly in storage.
Where these numbers come from
- USDA Plant Hardiness Zone Map (2023 revision). Zone assignment and the 30-year normals behind every cold-hardiness figure.
- NOAA NCEI 1991-2020 Climate Normals. Frost dates, growing-season length, and the probability bands on both.
- Cornell, UMN, and UC Davis Cooperative Extension crop guides. Spacing, days to maturity, soil pH targets, and per-plant yield ranges.
- USDA FSIS / FDA Produce Safety guidance. Wash, cure, and cold-storage handling numbers.
Ranges are regional guidance, not a promise for your yard. Your own logged results always override the published range.