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Ask Ruth September 2012: Harvesting Sweet Potatoes

September 28, 2012

Dear Ruth,

 This is the first year I have grown sweet potatoes. How will I know when they are ready to harvest?

Thanks,

Jennifer
Canton. NC

Dear Jennifer,

Yum! You’re looking forward to a harvest you will enjoy for months. Here are some factors to consider prior to your sweet potato harvest:

  • Determine when you planted your sweet potatoes. They take about 95 days to mature – so count back to when you planted them and decide when you can safely dig them up. If you planted near June 1st, your crop is ready to harvest.
  • The longer you leave sweet potatoes in the ground, the larger they will get…and sometimes they get gigantic. Do you want football-sized sweet potatoes?
  • Harvest when the weather is still hot, because sweet potatoes cure faster in hot weather.
  • Harvest before frost. Even though sweet potatoes can take a light frost, some of your tubers could be damaged.
  • Harvest when the soil is dry for best curing.
  • Harvest when you have ample time to complete the job. Sweet potatoes can develop sunscald if left in the sun for several hours.
  • Slowly-yellowing leaves on your sweet potato plants indicate that your potatoes are ready for harvest.

So Jennifer, balance the above considerations to figure your best harvest window. Leave your sweet potatoes in the ground at least 95 days, but don’t wait too late to harvest – because sweet potatoes will not cure as quickly in cool weather. You can always dig up one plant to monitor how the potatoes are looking.

Harvesting:

Sweet potatoes must be handled gently to prevent bruising. Using a potato fork, dig about 8-10” away from the main stem of the sweet potato. Once you have loosed the soil all around the potatoes, feel around with your hands for your tasty treasures. Gloves can make this easier. Set any nicked potatoes aside to eat quickly. Do not store injured potatoes with your good potatoes, or you will be faced with a smelly science project. Potatoes can be stored in corrugated cardboard boxes.

Curing:

Right after harvest, sweet potatoes should be cured. Proper curing “sets the skin” and heals minor injuries. Ideal conditions – high temperatures and high humidity – will allow the potatoes to cure quickly so any superficial wounds will heal. Sweet potatoes will cure in about a week in temperatures around 85 degrees Fahrenheit with a humidity level of 85-90% (Hey wait…that sounds like summer in the South!) Curing is much slower in cooler temps, and can take 4-6 weeks. During the curing process, provide adequate ventilation, protect potatoes from too much light and moisture, and don’t let them get too hot or too cold.

According to NC State, “proper curing has been shown to increase the sensation of moistness and sweetness, enhance the aroma, and decrease starch content while increasing sugars.” Sweet potatoes prefer temperatures around 55 degrees once they are cured. Temps below 50 degrees can actually DAMAGE your potatoes. Colder temps can cause the sweet potato to discolor, cause various root rots and pithiness, and later on – may prevent sprouting when you want “seed” for next year’s crop. Don’t store sweet potatoes in your refrigerator, in cold garages, or anywhere below 50 degrees. However, if your potatoes get too hot they will start sprouting prematurely, which will diminish the quality of the potato and shorten their storage life.

Does the above curing process seem too complex? I think you will have fairly good luck if you gently harvest your sweet potatoes, and store them in a cardboard box or a brown paper bag in a dark spot that is not too hot and is not colder than 55 degrees.

More:

  • Harvest all tender veggies before frost (peppers, tomatoes, eggplant, etc.).
  • Harvest basil before evenings are cool, or the leaves will turn black and become unusable. Preserve extra basil by making pesto or drying the leaves for winter use.
  • Let green gourds frost on the vine.
  • Many fall veggie plants (greens, spinach, some lettuces, etc.) can handle a light frost initially, but enjoy the protection of floating row covers or cold frames as fall progresses. Frost is reputed to make greens, like collards, taste sweeter.

Jennifer…I hope your sweet potato pie is delicious!

Best wishes,

Ruth

Gardeners: Got a Question for Ruth? Email us, or you can leave comments at the end of this article.

 Ruth Gonzalez is a former market farmer, gardener, local food advocate, and founder of the Tailgate Market Fan Club where she blogs at http://tailgatemarketfanclub.wordpress.com.   In her job at Reems Creek Nursery, Ruth offers advice on all sorts of gardening questions, and benefits daily from the wisdom of local gardeners.

Ask Ruth © 2012 Ruth Gonzalez & Organic Growers School

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