University of Vermont Extension
Department of Plant and Soil Science
HARVESTING SWEET POTATOES
Dr. Leonard Perry, Extension
University of Vermont
potatoes are becoming increasingly popular as they’re tasty and
nutrition. One cup of sweet potatoes
provides beta-carotene, over 4 times the daily need for vitamin A,
nutrients. One sweet potato plant can yield on average 2-1/2 pounds
or 100 pounds or more from a 20-foot row. If you tried growing your
own, as I did this
year in gro-bags (large 15-gallon fabric bags, filled with a topsoil
compost mix, good for patios and decks), you may be wondering when
and how to store them properly.
potatoes will continue to grow, as long as soil temperatures on
remain above 65 degrees (F), or tops are killed by frost. You can
check soil temperatures with an
expensive thermometer for soils or compost, available at many
supply stores or online (good to have around the garden anyway). You
around and check roots for proper size, too.
Even if leaves begin to yellow, leaving roots in the ground helps to
improve the yield and nutrition.
of timing and size, if tops have been killed by frost, you should
at once or they’ll quickly rot from disease entering from the dead
tops. If you can’t get the roots dug right after a
frost, cut the killed tops off just above the soil line, and you can
the roots in the ground for a few days.
care when harvesting, as the sweet potato roots can be damaged very
easily. They don’t have a protective
hard layer as do the tubers of white potatoes.
Wounds on sweet potato roots aren’t good, as they often lead to
can use a spade to dig roots, but many prefer a spading fork as
there is less
chance to damage the roots. Loosen the
soil, and dig around with your hands (I like to use gloves) for the
roots. Since roots can grow a foot away from the
plants, allow for this when digging.
It’s easier to harvest in dry soil than wet. You can gently wipe or
brush excess soil off,
but don’t wash the roots until you’re ready to use them. Don’t
leave roots in direct sun more than a
best storage, and to protect against any rots from abrasions and
should be “cured.” To do this, keep
roots dark, warm (80 to 85 degrees) and humid (85 to 95 percent
humidity) for 4 to 7 days.
should resist the temptation to dig and immediately eat sweet
fresh ones are more starchy than sweet, and don’t bake as well as
cured ones. Wait at least three weeks before eating, so
the starches can convert to sugars.
potatoes can last six months or more in storage, if held properly.
Ideal conditions are the same as for winter
squash—just slightly cool (55 to 60 degrees) and with a moderate
humidity (60 to 75 percent). Much below
55 degrees and sweet potatoes (similar to winter squash) will suffer
injury. Such injury appears as sunken, dark areas on the surface and
on the insides.
roots have holes, as if damaged from feeding, there could be a
causes. Voles love sweet potatoes, as do
larvae of wireworms in the soil. Adults
lay eggs in the spring, which lead to the larvae. Since they can
live for several years in the
soil, waiting for the right crop to come along and before feeding,
rotation to non-susceptible crops (not grasses, corn, potatoes of
or other root crops) helps to control wireworms and other problems.