Vegetable · Convolvulaceae
Sweet Potato
Ipomoea batatas
Give it heat, bright sun, and a long summer, and the sweet potato piles the ground with roots.
Full sun
Every 5–7 days
64–95°F · 18–35°C
90–120 days
Overview
Here is a crop that gives back. The sweet potato is a heat-loving vine that races across a bed and stashes plump storage roots underground while you barely lift a finger. It belongs to the morning glory family, worlds apart from the nightshade Irish potato it only shares a name with. Turn it loose in a long, warm summer and a few plants will fill a whole bed.
Once it hits its stride, this vine just runs. The stems stretch 3 to 15 feet (90 cm to 4.5 m) and blanket the ground, crowding out weeds while the real haul swells below. Better still, the harvest starts up top, because the young leaves and shoot tips cook up like spinach in kitchens all over the world.
Heat is the fuel that makes it all happen. Cold soil stops it cold and frost wipes it out, so hand it a warm bed and a long, hot summer and let the roots bulk up underground. Wait for the weather and the payoff is worth every day.
Care
The short version: plant it in full sun on loose, well-drained soil heaped into a ridge, pour on about 1 inch of water a week and dial it back near harvest, and feed light with low nitrogen so the plant throws its energy into roots, not runaway leaves.
Light
Sweet potatoes crave full sun, six to eight hours of it, to power the vine growth that pumps up the roots. They will tolerate a bit of afternoon shade, but pour on the sun and the harvest underground only gets bigger.
Water
Soak them deeply to about 1 inch a week and let the surface dry between drinks. Back off as harvest closes in, because a big gulp after a dry stretch makes the roots swell in a rush and split.
Soil
Plant into loose, well-drained loamy or sandy soil and mound it into ridges so the roots stretch out and never sit soggy. Hit a slightly acidic pH of 5.5 to 6.5 and they take off.
Temperature
This tropical crop thrives on real heat, right in the 64°F to 95°F (18°C to 35°C) sweet spot. Cold soil grinds it to a halt and frost finishes it, so let spring warm up before it goes out.
Humidity
Ordinary summer humidity in the 40% to 70% range is all it needs, and outdoors the number barely matters. Heat and sun do the heavy lifting for this crop, not the moisture in the air.
Feeding
Go easy and it pays you back. Work a low-nitrogen fertilizer like 5-10-10 into the bed before planting, then sidedress once before the vines cover the row. Overdo the nitrogen and you grow a jungle of leaves and shortchange the roots.
Pruning
Forget pruning for the roots. Snip the vines only to tidy a bed or curb a wanderer, and put the tender shoot tips straight into the pot as cooked greens.
Size & spacing
The plants stay short at 6 to 12 inches (15 to 30 cm), but the vines charge out 3 to 15 feet (90 cm to 4.5 m) wide. Hand each one room to sprawl, or steer the runners back so they leave their neighbors alone.
When to plant
It all runs on heat, and frost calls a hard stop, so nailing the timing sets you up for a great crop. Sprout slips indoors off a stored root in late winter, send them out once spring warms the soil, and dig the roots in fall before frost lands. Hit that window and the plant rewards you.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: Sprout slips from a stored root indoors 6-8 weeks before transplanting
- Plant: After all danger of frost once soil is warm, roughly April through early July
- Harvest: Harvest storage roots in fall before the first frost
Hardiness
USDA hardiness zones: 9–11
Temperature: down to -7°C
Troubleshooting
Almost every sweet potato problem hides underground and only shows itself on the roots at harvest, which keeps the growing season refreshingly carefree. Get to know the handful of pests and the one fungus below and you will pull clean roots year after year. Spot your match, act fast, and stay a step ahead for next season.
Stem-end pinholes and dark, bitter tunnels
Meet the sweetpotato weevil, the crop's number-one enemy. Adults punch small holes near the stem end and the larvae drill through the flesh, packing frass into tunnels that leave the root dark and bitter. Dig out and destroy every infested root and vine, and never hang onto that material for next year's slips.
Fix:
- Remove and destroy infested roots and vines
- Do not save infested material for propagation
Ragged holes drilled into the roots
Say hello to wireworms, the wiry larvae of click beetles that gouge shallow pits and deepen them into ragged holes as the roots grow. They swarm ground fresh out of grass, so give sod a wide berth. Harvest the second the roots size up and you slam the door on their feeding.
Fix:
- Harvest promptly once mature to limit feeding time
- Avoid planting in recently turned sod
Dark blotches racing across the root skin
Good news, scurf is a fungus that stops at the skin and never bites deeper. The dark spots spread and merge, but the flesh below stays sound and ready to eat. It sneaks in on infected planting stock, so cull the worst roots and fire up the next crop from clean, disease-free slips.
Fix:
- Discard heavily affected roots
- Start next crop only from clean, disease-free slips
Toxicity
Here is more good news to love about this crop: it is completely safe for people and pets. The ASPCA lists the vine as non-toxic to cats, dogs, and horses, and the cooked root and tender greens land on plates for people and animals alike. Grow it anywhere without a worry.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
Great company for a cat. A nibble of vine will not poison it, though a big mouthful of any greenery can bring on a little drool or a quick upset stomach.
Dogs None
Nothing toxic here at all, and cooked sweet potato already stars in loads of dog foods. Keep servings sensible, since a bellyful of fibrous root or vine can loosen the stool.
Horses None
Horses can graze the foliage with zero poisoning risk. As with any rich new feed, bring it in slowly so the gut catches up.
Rabbits Safe
The leaves and vine tips make safe forage, and a little cooked root goes down fine. Keep the starchy root in check, because too much at once can upset a rabbit's sensitive gut.
Livestock Safe
Cattle, goats, and sheep tuck into the vines and roots with no trouble, and growers raise the foliage as fodder in loads of regions. Keep clean water flowing and switch the feed over gradually to keep things smooth.
Birds Safe
Chickens and other poultry pounce on cooked root and chopped greens with no danger. Serve it as one part of a varied diet, not the whole spread.
People Safe
For people, cooked sweet potato is a nourishing staple, and the young leaves and shoots make a fine cooked green. Dig in freely, just remember the raw root is tough to digest in big amounts.
Although non-toxic, eating large amounts of any plant material can cause mild stomach upset in pets.
Varieties
Hundreds of cultivars are out there to explore, but a few orange-fleshed champions show up in most gardens. Start with these standout names.
Beauregard
A garden favorite with orange flesh that pumps out heavy yields and races to maturity earlier than most.
Covington
An NC State star, rose-skinned and orange-fleshed, that delivers even, dependably sweet roots every time.
Georgia Jet
A speedy orange-fleshed type built for shorter, cooler seasons that leave slower varieties stranded.
How to propagate
Skip the seed packet, because sweet potatoes launch from slips, the eager sprouts a single stored root pushes out. Coax a few grocery tubers into growth and turn them into a whole bed of plants for nothing.
Stem cuttingsEasy
Spring, after the soil has warmed and frost danger has passed · 2 to 3 weeks
Sweet potatoes take off from slips, the rooted sprouts you snap from a stored root once it starts shooting. Plant them out as cuttings the moment spring soil warms and frost clears, and they dig in and root fast, usually within 2 to 3 weeks.
Myths
The whole sweet potato plant is poisonous because it is kin to the toxic morning glories.
Not a chance, because the roots and cooked leaves of the food sweet potato feed people across the globe, and the ASPCA rates the plant non-toxic. The mix-up starts with the seeds of certain ornamental morning glories, which are separate Ipomoea species and a whole different story.
Sweet potatoes and everyday Irish potatoes are the same kind of plant.
Not even close cousins. The sweet potato scrambles through the morning glory family and swells its roots into storage organs, while the Irish potato sticks with the nightshade family and grows its tubers on underground stems.