Curing Sweet Potatoes: How to Make Them Sweet and Store for Months

Why curing is not optional

Dig a sweet potato, bake it that evening, and you will wonder what the fuss is about: it tastes bland, dry and starchy. The sweetness people associate with the crop is not present at harvest. It develops during curing, when enzymes inside the root convert stored starch into sugars, and it continues to develop slowly in storage for weeks afterwards.

Curing does a second job that matters just as much. Every root comes out of the ground with scrapes, fork nicks and torn skin where it broke away from the crown. Warm, humid air prompts the root to lay down a corky layer over those wounds within a few days, which is what stops rot organisms entering. An uncured root keeps for two or three weeks. A properly cured one keeps for six months or more.

Digging without damaging the roots

Curing can heal a clean scrape but it cannot rescue a root you have driven a fork through. Dig on a dry day, ideally after the bed has been kept dry for three or four weeks, because roots lifted from wet soil bruise easily and cure poorly. Cut the vines away and take them off the plot first so you can see what you are doing.

Start the fork a full twelve inches (30 cm) out from the crown and lever the whole ridge up from the side rather than digging down into it. The roots radiate much further than you expect. Lift the crown by hand, tease the roots apart, and leave them lying on the surface for two or three hours to dry off if the weather allows. Do not wash them and do not knock the soil off hard; brush it off gently after curing.

1. Stop watering three to four weeks ahead Dry soil at digging means firmer skin, less bruising and far better curing. Do not dig within two days of heavy rain if you can wait.
2. Cut and remove the vines first Clear the top growth away so you can see the crown. Take the vines off the plot rather than leaving them beside the row.
3. Lever from a foot out Push the fork in twelve inches (30 cm) from the crown and lift the ridge. Digging close to the crown spears the biggest roots every time.
4. Handle them like eggs Do not drop roots into a bucket or tip them from a height. Every bruise is a place rot starts. Lay them in a single layer in a crate.

Set damaged roots aside in their own crate as you dig. They will not store, but they are perfectly good to eat within a few weeks, and keeping them separate stops one wound spoiling a whole box.

The curing conditions: warm, humid, ten days

The target is 80 to 85F (27 to 29C) at 85 to 90 percent relative humidity for seven to ten days. It is a deliberately unpleasant combination, closer to a greenhouse at the height of summer than to anywhere in a house, and hitting it exactly is less important than getting reasonably close. Warmer and more humid cures faster; cooler and drier takes longer and works less well.

Air still has to move. Roots packed tight in a sealed box in that heat will simply rot, so what you want is high humidity with gentle ventilation, not a sealed container. Single layers in ventilated crates, stacked with a gap between them, is the arrangement to aim for.

Practical ways to hit those conditions at home

Very few gardens have a curing room, so the job is improvisation. The most reliable domestic approach is a spare room or airing cupboard with a small heater and a bowl of water, or a cheap plastic greenhouse in a warm spot. In a warm climate a shaded porch does it with no equipment at all. Whatever you use, put a thermometer in with the roots rather than guessing.

The commonest homemade method is crates lined loosely with newspaper and covered with a sheet of plastic or a damp towel, left in the warmest room of the house. The covering traps the moisture the roots themselves give off, which is usually enough to raise humidity to the right range. Lift the cover for a few minutes each day to change the air and to check nothing is going soft.

1. Single layers in ventilated crates Do not pile roots deep. One or two layers per crate lets warm air reach every root and lets you spot a rotting one early.
2. Cover to hold humidity, not to seal Drape plastic or a damp cloth over the crates with the sides left open. A sealed box turns curing into rotting.
3. Put a thermometer in the crate Measure among the roots, not on the far wall. Aim for 80 to 85F (27 to 29C) and adjust the heat source accordingly.
4. Check daily and pull out any softening Look over the crates each day. Remove anything soft, weeping or smelling sour immediately, before it reaches its neighbors.

Storage after curing, and never the refrigerator

Once cured, move the roots somewhere cool but not cold: 55 to 60F (13 to 16C) at moderate humidity is the target, which suits a cool cupboard, an unheated back room or a frost-free garage. Wrap each root in newspaper or lay them in crates with paper between the layers, keep them dark, and keep them away from anything that gives off ethylene, which brings on sprouting.

Refrigeration is the one thing that genuinely destroys them. Below about 50F (10C) sweet potatoes suffer chilling injury: the flesh develops a hard core that never softens in cooking, the flavor goes flat, and the roots decay far faster once brought back to room temperature. Note the digging date and the date you finish curing, and taste one root a month; you will find the flavor keeps improving for the first eight weeks or so, and that record tells you when your own crop is at its best.

1. Move to 55 to 60F (13 to 16C) Cool, dark and dry, with some air movement. A cellar, cool cupboard or frost-free garage all work.
2. Wrap individually and keep dark Newspaper around each root cushions it and stops one going soft against another. Light triggers greening and sprouting.
3. Never refrigerate an uncooked root Chilling injury below 50F (10C) causes a hard core and off flavors. Once cooked, leftovers are fine in the fridge.
4. Record dates and taste monthly Note when you dug, when curing ended, and how each monthly taste compares. After one season you will know exactly how long to cure for your own conditions.