Friday, May 10, 2013

VEGETABLE SPOTLIGHT: Sweet Potatoes - NC Crop, Home-Growing, & Vodka!

North Carolina Piedmont growing varieties of Sweet Potatoes.
Photo: Leanna Murphy Dono.
Contributed by:
Leanna Murphy Dono and Marsha Booker-Hibbs (GM)
Durham Co. Extension Master Gardener Volunteers

Q. Do you know the difference between a sweet potato and a yam?
A. Sweet potatoes, aka. Ipomoea batatas, hail from the scientific family Convolvulaceae (a Morning Glory relative), and they originated from the South American regions of Peru and Ecuador. Sweet potatoes are regularly grown in US, plus they contain HIGH Vitamin A, and more commonly an orange flesh.
Yams, on the other hand, hail from the Dioscorea family of woody vines and shrubs and originated from West Africa and parts of Asia. Currently the US only imports them from the Caribbean, they are LOW in Vitamin A with exclusively white flesh.

Q. Does the USDA know the difference between the two vegetables?
A. NO!!! The USDA (confusingly) requires that Sweet Potatoes also be labeled as Yams in our grocery stores!

Ipomea batatas have been an often overlooked and extremely nutritious choice of vegetable. Sweet potatoes are an excellent source of: Vitamin A, Vitamin C, fiber, potassium, calcium, are a low Glycemic Index food, and provide even better nutrition if you eat the peel!
If you are a vegetable gardener and contemplating adding sweet potatoes to your crop this year, then plant the slips now! Sweet potatoes are a 100-day growing season plant, best suited to growing in raised beds, and their roots grow at least 6” deep.

Yield - If you were to plant 12 slips at 12” apart, the 12 slips would yield about 25-30 lbs. of sweet potatoes in one season! (For gardeners with limited space, two slips will grow in a container at least 15” wide and deep and yield 2-4 lbs. of roots.) It is also best practice to rotate sweet potatoes with corn plantings from year to year to reduce opportunities for wireworm and nematode infections.

Plant in full sun (West or Southern exposure ideal). Water regularly! This is critical for first 45 days for root formation. Give minimum 1” per week (but don’t over-water). Plant in well-drained soil to prevent root rot, and use disease- free slips. Apply fertilizer high in phosphorus for root growth; use a 10-20-10 granular at planting, use 15-30-15 liquid after four weeks.

Production Timeline:
Container of 'Porto Rico' sweet potatoes.
Photo: Leanna Murphy Dono
April 1 – order your slips and prepare beds
May 1 Plant Slips (after last frost)
September 1 – no irrigation 3 weeks (prep to dig)
 October 1 Dig and harvest (before frost!)
1 week – Cure at 80-85°F /90% humidity
November 1 to March 1 Store at 55°F and eat!
Varieties and Cultivars of Sweet Potatoes:
Orange Flesh
Georgia Jet:  High yield – prone to cracking
Carolina Ruby:  Store well without shrink
Hernandez:  grows 120 days; grows well in sandy soil
Beauregard:  Most common, but disease challenges
Covington:  Developed at NC State University and disease resistant
Porto Rico:  Best container-grown sweet potato, “superior eating flavor”
White and Purple flesh
O'Henry: High Yield w/jumbo tubers, L-O-N-G vines – 60”+
Muraski: L-O-N-G vines – 60”and disease resistant
Japanese: Short vines – 40” and 125+ days to mature!

Harvest and Curing:
Know your potato variety and the length of time to mature. Dig the potatoes with spade.  It’s important not to give plants any irrigation three weeks prior to harvest which would dry out roots. Dig and harvest by Oct. 1 (before killing frost!). Throw out any culls. No splits, holes or insect damage (eat these “green”). Shake off excess dirt, but do not wash. Cure indoors in the dark for 5-10 days at 80-85°F and 90% humidity. This gives roots time to seal skin and heal any cuts. Watch for any condensation – they should be dry. Curing triggers the sugar producing enzymes.
When to Use when either “GREEN” = freshly dug, un-cured sweet potatoes - immediately use after harvest, they are excellent for candying or sweetened pies/casseroles.
“CURED” means that sweet potatoes were allowed to dry and ripen in warm, humid temperatures for maximum flavor. Use 6-8 weeks after harvest. These potatoes are best for baked, mashed, canning, frying, etc.

IDEAL STORAGE: 55°F with moderate humidity (85%). For example, store in an unheated garage in slatted crates or baskets with ventilation. If sweet potatoes are stored in refrigeration or below 50°F, the roots develop hard centers and diminish flavor. Conversely, temps higher than 60°F encourage sprouting and root weight shrink.

Diseases and Pests:
SWEETPOTATO HORNWORM = Eats foliage and that reduces yields or root size
TORTOISE BEETLES = Eat foliage; attack newly planted slips or plants under stress. Can transfer from ornamentals
DEER = Eat foliage and that reduces yields or root size Source: AG-295, NC State Center for Integrated Pest Management
SPRING ROSE BEETLE & JAPANESE BEETLE = larvae/grubs feed on roots
FLEA BEETLES = Adults eat foliage; larvae eat roots, etch shallow, winding trails and cause splits
SMALL FRUIT FLIES = feed on decaying vegetables and lay maggots in splits (harvest and cure only good roots)

Pests, especially deer, have long been attracted to the ornamental cultivars such as Ipomoea batatas ‘Margarita’, ‘Blackie’ and ‘Sweet Caroline’. These cultivars are ornamental, annual varieties grown primarily for foliage. They may or may not produce potatoes, but if they do, the potatoes are likely bitter-tasting, but they could certainly over-winter for growing slips in the Spring.
Fun Facts about Sweet Potatoes and North Carolina:
  • Since 1971, North Carolina ranks as the No. 1 sweet potato producing state in the United States. NC annual harvest constitutes about 40-50% US supply.
  • Sampson, Nash & Johnston counties alone produce about ½ of NC yield.
  • 1996 Ms. Celia Batchelor’s 4th grade students in Wilson (aka “The Tater Tots”) successfully lobbied for Sweet Potatoes to be named the official State Vegetable.
  • 16th Annual Sweet Potato Festival in Rockford, NC September 21, 2013 from 10-5 p.m.
  • North Carolina restaurants are serving up a great variety of dishes on their menus: sweet potato fries, baked sweet potatoes with bacon and white cheddar, candied fried sweet potatoes, sweet potato coconut milk soup, sweet potato cheesecake, pork chops stuffed with thyme and sweet potatoes, and sweet potato biscuits.
  • NC Home-Grown Covington Sweet Potato Vodka: 20 lbs. of NC sweet potatoes go into every bottle; distilled in Snow Hill, NC; vodka won a prestigious gold medal at the 13th annual World Spirits Competition in March 2013. in San Francisco; the Covington sweet potato was developed by NC State University. 

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