Vegetable / Warm season
Sweet Potato
Grown from slips, cured in the kitchen, eaten all winter
Plant out byJun 1zone 6
- Family
- Morning glory (Convolvulaceae)
- Sun
- Full sun (6+ h)
- Difficulty
- Easy
- Days to harvest
- 90-120 days
- Spacing
- 12 in apart, rows 36 in
- Pot size
- 10 gal pot (fine in pots)
- Frost
- Tender
- Start
- Start indoors
- Water
When to plant
Showing .
Averages for a typical garden in the region. Your local frost dates may differ by 2-3 weeks, check a local source.Too late this year (try fall)
In zone 6, start seeds indoors Feb 23 to Mar 9; plant out May 11 to Jun 1. Average last frost Apr 20, first fall frost Oct 20.
Units
Nobody plants sweet potato seeds. You plant slips, which are rooted sprouts grown off an old sweet potato. You can buy them. Or stand a root in a jar of water about eight weeks before your last frost, and twist off the shoots once they reach 6 to 12 inches. My kids checked the jar every morning like it was a science fair.
Cold is the real enemy here. Slips go out three to four weeks after your last frost, once soil is above 65 degrees F and nights hold above 55. Plant early and they sit still or rot. The same goes at the far end of summer: dig before the first fall frost, because chilled roots go off in flavor and spoil in storage. Wireworms can scar the roots, and they tend to be worse in beds that were lawn the year before.
Once the vines take off, there is little to do. They handle dry spells better than most crops, though steady water in the last month helps roots size up. Space slips about a foot apart in rows 3 feet apart, or use a big tub: a 10-gallon container holds two or three plants. Then cure the harvest somewhere warm for about two weeks. Fresh-dug roots taste starchy, and curing is what sweetens them.
Things to consider
- The vines spread several feet and can root where they touch soil. Give them a corner to roam, or lift the runners now and then so they stay off the paths. Bush varieties take up far less room and suit tubs and small beds.
- Dig with a fork, starting well out from the crown. The skin is thin at harvest and bruises easily, and nicked roots rot faster. Let them dry on the soil for a few hours before you move them inside to cure.
- Store cured roots around 55 to 60 degrees F, never below 50 and never in the fridge. A closet on an inside wall often does the job. Cured and stored well, roots often keep for several months.
Good neighbours
Pests to watch for
WirewormsFlea beetlesSweet potato weevilsRoot-knot nematodes
Questions about growing sweet potato
Are sweet potato leaves edible?
Young leaves and shoot tips are cooked as a green in many parts of the world. Take a few from each plant so the roots still get enough leaf. They taste mild once cooked. Pick them in the morning, when the leaves are crisp.
How do I know when sweet potatoes are ready to dig?
Most varieties need 90 to 120 days after planting. Leaves and vine tips start to yellow near the end, and you can dig one test plant to check root size. Always finish before frost. Nights below 50 degrees F can already harm roots still in the ground, so watch the early fall forecast.
Can I grow sweet potatoes in a short northern summer?
It is harder, but a fast variety and black plastic to warm the soil can get you there. Ask your local extension office which varieties do well in your area. A tub on a hot patio can also beat a cool bed. Plant slips a little late rather than early, since cold soil sets them back more than a short delay.
Save this crop
Pin it to a garden board so it is there when planting time comes round.
Similar crops
Sources
General guidance for home gardens. Frost dates are averages for a zone or region; check a local source (in the US your county extension office) for local timing.