Missouri · zones 5b–7a
When to plant sweet potatoes in Missouri.
Sow or transplant between May 22 to Jun 18 in a typical year, keyed to Missouri's median last frost around Apr 15. Dates below are state medians; your ZIP code shifts them by days to weeks.
The 2026 windows
Sweet Potatoes dates for a typical Missouri season.
1 · Start indoors
Apr 10 to May 7
About 6 weeks before set-out. Warm spot, real light.
2 · Set out
May 22 to Jun 18
Keyed to the ~Apr 15 last frost. Sow 3" deep, 14" apart.
Harvest
~110 days later
~2.5 lb per plant over ~1 weeks.
Missouri spans more than one climate: Zone 6 is the most common zone, but the state runs 5b to 7a. That's why the planner works from your ZIP code's frost dates, not your zone: mountain and coastal gardens in the same state can be three weeks apart.
Missouri growing notes
The Bootheel grows sweet potatoes on sand. The rest of Missouri needs a mound.
Two different Missouris, two different beds
The Bootheel, southeast Missouri's boot-shaped extension along the Mississippi River, sits on the same deep sandy loam that made it serious row-crop country, and that soil happens to be close to ideal for sweet potatoes: loose enough that the roots swell into a smooth, even shape instead of forking around obstructions. Gardeners on Ozark chert or heavy river-bottom clay elsewhere in the state do not have that luxury and need to build it: a mounded ridge 8 to 10 inches tall and 12 inches wide gives the roots the same loose, warm profile the Bootheel provides for free.
Set slips, the rooted cuttings this crop is grown from rather than seed, 14 inches apart along the ridge with the bottom 2 nodes buried and the top leaves above ground. There is no seed-style germination gate to watch for here; slips simply wait until the ridge itself has warmed past frost and holds around 65 degrees before they go out, and Missouri's long, roughly 188-day season gives enough margin over the 110 days this crop needs that there is no reason to rush it into cold ground.
The pests are borrowed from the potato patch
Sweet potato and true potato are unrelated plants, and their pest lists separate more cleanly than most Missouri gardeners expect. Colorado potato beetle feeds only on the nightshade family, so it will strip an Irish potato row down the path and never cross to a sweet potato vine, whatever the two crops look like growing side by side. Aphids do move between them, clustering on tender vine tips through a humid stretch, and a weekly look at the undersides of new leaves catches a colony while hosing it off still works.
Sweet potato skips the rest of the potato disease list the same way it skips Colorado potato beetle: it belongs to the morning glory family, not the nightshades that late blight needs to infect. The real trouble in a wet Missouri summer is a solid mat of vines holding damp ground underneath for days on end; pull the mat apart after a heavy rain so leaves and soil actually dry out. Vines that cover the ground densely by late summer are otherwise a good sign, since dense foliage is what shades out weeds for the rest of the season.
Curing wants the opposite conditions garlic does
Dig sweet potatoes gently with a fork before the first fall frost, since a single freeze on the exposed vines can spread cold damage down into the roots within a day and ruin storage life. Handle the roots carefully; sweet potato skin bruises and scrapes far more easily than a true potato's, and any broken skin becomes a rot entry point in storage.
Then cure them somewhere warm and humid: a stretch of 4 to 7 days at 85 degrees, with the air staying muggy, 90 percent humidity or better, is what heals the skin over. That is the exact opposite of the cool, dry, airy spot garlic wants and easy to overlook if you grew both crops the same fall. Curing converts starch to sugar and heals over any nicks from digging; a properly cured Bootheel or backyard sweet potato then keeps 4 to 6 months in a cool spot around 55 to 60 degrees, considerably longer than an uncured one, which softens within weeks.
In Missouri: watch for
The pests that find sweet potatoes here.
A middle-length season, about 188 frost-free days, means sweet potato overlaps wireworms & white grubs for a stretch each summer. Check plants every week or two and treat early.
Wireworms & white grubs
Shallow holes and grooves chewed into the roots, found only at digging time.
Organic fix: Avoid planting into ground that was in sod last year; rotate away from grassy beds.
Clusters on the tender growing tips of new vines.
Organic fix: Hose them off in the morning, or use insecticidal soap.
Black rot
Dry, firm dark patches on the roots, usually found at harvest or in storage, with a sweet fruity smell.
Organic fix: Start from clean slips cut well above the soil line, never save roots from a bad crop, and rotate 3 years.
Your season math: Missouri gives sweet potatoes about 188 frost-free days, and it needs roughly 110 days to a first harvest. It's a one-planting crop, so time that single sowing well.
Planting sweet potatoes in Missouri: questions
When should I plant sweet potatoes in Missouri?+
In a typical Missouri year, sow sweet potatoes or set out transplants between May 22 to Jun 18, keyed to the state's median last frost around Apr 15. Your exact dates shift with your ZIP code and microclimate.
When do I start sweet potatoes seeds indoors in Missouri?+
Start seeds inside about 6 weeks before set-out: roughly Apr 10 to May 7 for a typical Missouri season.
What USDA zone is Missouri?+
Missouri spans zones 5b–7a, mostly zone 6. But frost dates, not zones, set planting time. The free planner uses your ZIP code's actual frost dates.
How many sweet potatoes plants do I need?+
Depends who you're feeding. The crop page has exact counts per household size, or the free planner does the math for your family in about 60 seconds.