When to Plant Sweet Potatoes by Zone (Slips, Timing & Tips)

Sweet potatoes are a warm-season crop that needs heat, patience, and a long growing season. They're not related to regular potatoes at all — they're actually in the morning glory family — and they grow differently too. You plant slips (rooted sprouts), not seed pieces. Get the timing right and you'll be pulling gorgeous orange tubers out of the ground in fall. Get it wrong and you'll have lots of vine and very little to eat.

Sweet potato planting dates by zone

The critical rule: soil temperature must be at least 65°F (ideally 70°F+) at 4 inches deep before you plant slips. Sweet potatoes planted in cold soil just sit there and rot.

Check your seasonal planting calendar to see how sweet potatoes fit alongside your other crops.

Can you grow sweet potatoes in zones 3–4?

It's possible but challenging. Your growing season is short, so you need to:

• Choose short-season varieties (90 days): Beauregard, Georgia Jet, or Covington
• Pre-warm the soil with black plastic mulch for 2–3 weeks before planting
• Use row covers or low tunnels to add warmth
• Plant slips as soon as soil hits 65°F — usually late May to early June
• Harvest before the first frost — sweet potato vines are killed by any frost

It's doable. You won't get the yields that zone 8–10 growers get, but 3–5 pounds per plant is achievable even in zone 4 with the right approach.

Getting slips

Buying slips

The easiest approach. Order from a reputable online nursery (they'll ship at the right planting time for your zone) or buy from a local garden center. Plan to buy 12–25 slips for a 25-foot row, which should yield 30–50+ pounds of sweet potatoes.

Growing your own slips

Start 6–8 weeks before your planting date. Here's the process:

1. Place a whole sweet potato (organic, not treated with sprout inhibitor) in a jar of water with the bottom third submerged. Use toothpicks to prop it up.
2. Keep in a warm spot (75–80°F) with indirect light.
3. Sprouts will emerge in 2–4 weeks. When they're 6–8 inches long, twist them off the potato.
4. Root the slips in water for 5–7 days until roots are 1–2 inches long.
5. Harden off for a few days, then plant outdoors when soil is warm enough.

One sweet potato can produce 8–15 slips. For our guide on starting plants indoors, see the indoor seed starting schedule.

How to plant sweet potato slips

• Spacing: Plant slips 12–18 inches apart in rows 3–4 feet apart. Sweet potato vines spread aggressively.
• Depth: Bury the bottom 3–4 inches of each slip, leaving the top leaves exposed.
• Raised rows or mounds: Sweet potatoes do best in loose, raised soil (8–12 inch mounds or raised rows). This improves drainage and makes harvesting easier.
• Water well after planting: Give each slip a thorough soaking. Keep soil moist for the first week while roots establish, then reduce watering.

Growing tips for bigger yields

• Full sun is essential. Sweet potatoes need 8+ hours of direct sun. Shady spots produce vines but few tubers.
• Black plastic mulch in cooler zones (5–7) keeps soil warm and suppresses weeds. It can add 10–15 days of effective growing season.
• Don't turn the vines. Old advice says to lift and turn vines to prevent them from rooting at nodes. Modern research shows this actually reduces yields. Let them be.
• Water moderately. Sweet potatoes are drought-tolerant once established. Overwatering, especially in the last month, causes cracking and watery tubers. Back off watering 3–4 weeks before harvest.

Harvesting sweet potatoes

Sweet potatoes are ready when:

• The leaves start to yellow (in zones with long seasons)
• You've hit the variety's days-to-maturity number
• Or frost threatens — harvest immediately before any frost touches the vines

Harvest carefully. Sweet potato skin is thin and delicate right out of the ground. Use a garden fork, starting 12–18 inches away from the plant's base, and work inward carefully.

Curing is essential

Fresh-dug sweet potatoes are starchy and bland. They need curing to develop sweetness:

1. Place unwashed sweet potatoes in a warm (80–85°F), humid spot for 7–10 days
2. A closet, spare bathroom, or covered porch works well
3. After curing, move to cool storage (55–60°F) — NOT the refrigerator
4. Properly cured sweet potatoes store 4–6 months

Best varieties by zone

Common problems

• Tiny tubers: Usually caused by planting too late, too much shade, or too much nitrogen fertilizer.
• Cracked tubers: Inconsistent watering — too dry then too wet. Keep moisture even during bulking.
• Voles and mice: They love sweet potatoes underground. Hardware cloth at the bottom of raised beds helps.
• Frost damage: Even a light frost kills the vines and can damage tubers near the surface. Check your first frost date and harvest before it hits.