When to Plant Sweet Potatoes

When to plant sweet potatoes: the key number

Plant sweet potato slips when soil temperature at 4-inch depth reaches 60°F and nighttime air temperatures consistently stay above 50°F. For most of the US, this falls 2-4 weeks after the last frost date — not the last frost date itself.

The last frost date is a starting point, not a planting date. Sweet potatoes need warm soil, not just frost-free air. Soil warms more slowly than air in spring. A 70°F afternoon with 45°F nights and 55°F soil is not sweet potato planting time.

Why soil temperature matters more than calendar date

Sweet potato slips planted in cold soil don’t grow — they stall and often rot at the crown. Cold soil allows fungal pathogens that attack vulnerable new growth. Each week spent in cold soil delays root initiation by 2-3 weeks.

Research from North Carolina State University Extension shows that slips planted at 65°F soil establish fully 10-14 days faster than those planted at 60°F. At 70°F+, establishment takes 5-7 days. The difference compounds: a slip that establishes in 7 days has a 3-week head start over one that took 21 days — and that extra growing time shows up directly in final root size at harvest.

Practical takeaway: if your soil is at 58°F, wait. If it’s at 62°F and nights are above 50°F, plant.

Use a soil thermometer, not a guess. Measure at 4 inches deep, mid-morning (not right after a hot afternoon or cold night), for 3 consecutive days.

Zone-by-zone planting dates

These are averages. Your microclimate, soil type, and sun exposure shift dates by 1-3 weeks. Clay soil warms 2-3 weeks later than sandy soil. North-facing slopes stay cold 4-6 weeks longer than south-facing ones.

Counting back from first fall frost

Sweet potatoes need 90-120 days from planting to harvest. Count backward from your average first fall frost to set a hard deadline for planting.

Example for Zone 6b (Nashville area):

• First frost: October 15
• Variety: ‘Beauregard’ (90 days)
• Deadline planting date: October 15 minus 90 days = July 16

So any planting before July 16 gives a full-season crop. The sweet spot for Zone 6b is late May to early June — this gives 100-120 days before frost, plenty of time for 90- or 100-day varieties.

For shorter seasons (Zones 3-5), use only 90-day varieties (‘Georgia Jet’, ‘Beauregard’) and focus on speeding soil warmth through raised beds and black plastic mulch.

How to get sweet potato slips

Option 1: Buy slips

Mail-order slips arrive ready to plant in April-June depending on your zone. Suppliers ship at zone-appropriate timing. Reliable sources include Sandhill Preservation Center, Southern Exposure Seed Exchange, and many local farm stands. Expect to pay $1.50-$4.00 per slip; order 2-3 slips per 10-foot row for a home garden.

Slips ship bare-root. Plant within 2-3 days of arrival, or store in a glass of water at room temperature for up to 1 week.

Option 2: Grow your own slips from stored tubers

This is the most economical approach for growers who saved roots from last season or bought sweet potatoes from the grocery store (check that they haven’t been sprout-inhibited — many commercial potatoes are treated to prevent sprouting).

1. Start 8-10 weeks before your target planting date.
2. Set sweet potato roots on a bed of moist potting mix in a warm location (75-80°F).
3. Cover loosely with plastic to hold moisture. Slips emerge in 3-6 weeks.
4. When slips reach 6-8 inches tall with several leaves, twist them off the parent root at the base.
5. Place slips in a glass of water for 1-2 weeks to develop roots before planting.

Each sweet potato root produces 5-10 slips.

Preparing the bed

Sweet potatoes perform best in:

• Sandy loam or loamy soil, not clay (clay compacts around developing roots and causes odd shapes)
• Loose, deep-tilled beds: till or loosen 12 inches deep
• pH 5.5-6.5: slightly acidic
• Full sun: 8+ hours of direct sun daily
• Good drainage: standing water causes root rot

Don’t add extra nitrogen. High nitrogen produces big, leafy vines and small roots. If your soil has had compost or manure added recently, no additional fertilizer is needed. If soil is poor, add a low-nitrogen fertilizer at planting (5-10-10 or similar).

Raised beds warm faster and provide excellent drainage. See our guide on how to grow sweet potatoes for bed construction details.

Planting slips

1. Dig holes or furrows 4-6 inches deep, spaced 12-18 inches apart in rows 36 inches apart.
2. Insert each slip so the bottom 3-4 inches of stem is buried. This buried stem forms roots where the eating tubers grow — more buried stem means more potential tubers.
3. Leave 2-3 leaves above soil.
4. Water immediately and thoroughly.
5. Cover with 2-3 inches of straw mulch or black plastic (weed control and soil warmth).

Slips wilt dramatically for 2-5 days after planting — this is normal. They’re establishing roots before the leaves can keep up with water demand. Do not overwater during this period.

Extending the season in short-season zones

Black plastic mulch

Black plastic laid over the bed 3-4 weeks before planting warms soil 4-8°F compared to bare ground. This can move planting date 2-3 weeks earlier in Zone 5-6 gardens. Plant through slits cut in the plastic.

Raised beds

A 12-inch-tall raised bed warms 2-3 weeks earlier than an in-ground bed. Combine with black plastic for maximum early warmth.

Row covers

Floating row covers (1.5 oz weight) protect slips from late frosts and moderate cold snaps for 2-3 weeks after planting. Remove once temperatures are reliably above 60°F nights.

For companion planting with sweet potatoes, see our sweet potato companion plants guide. For the full growing season overview, see sweet potato growing.

Harvest timing

Harvest before the first frost. A light frost (30-32°F) kills sweet potato vines immediately but doesn’t damage roots still in the ground — you have 2-3 days to harvest after first frost.

A hard frost (28°F or below) will damage roots in the ground. Harvest before the first hard frost regardless of vine appearance.

Signs roots are ready:

• Leaves yellow and begin to die back naturally (not frost-related)
• You’ve reached the variety’s rated days to maturity
• A test dig shows full-size roots (dig carefully, 12 inches from the vine center)

After harvest, sweet potatoes must be cured at 85°F with high humidity (80-90%) for 5-10 days before eating or storing. Curing converts starches to sugar (the characteristic sweetness) and heals surface cuts that allow rot.

Summary: your planting checklist

Before you plant sweet potato slips:

• Soil thermometer reads 60°F+ at 4-inch depth for 3 consecutive days
• Night temps consistently above 50°F
• 90-120 frost-free days remain before your first fall frost
• Bed is loose and deep (12 inches), well-drained, not recently nitrogen-fertilized
• Slips are 6-8 inches tall with visible roots at the base or water-rooted

The USDA Plant Hardiness Zone Map at planthardiness.ars.usda.gov gives your zone and informs both frost date lookups and variety selection.