Guidelines for Sweetpotato
and Transplant Production
Revised 9/90 -- Author
Reviewed 1/98 HIL-23-C
Jonathan R. Schultheis
Extension Horticultural Specialist
Department of HorticulturalScience
North Carolina Cooperative Extension Service
North Carolina State University
Sweetpotato production should be planned as a part of your total
annual farm management scheme. Sweetpotatoes should not be grown just
"once in a while" or just in those years you think you'll be able to
"get rich quick." Commitment to an ongoing production program is
required in order for you to be a successful grower.
Having your own good seed program indicates that you are committed
to sweetpotato production and gives you confidence in the quality of
the transplants you use for your crop. It gives you control over
transplant production by providing you with the freshness and
quantity you need when you want it.
The North Carolina Crop Improvement Association has been
certifying sweetpotatoes for more than 50 years. The North Carolina
Certified Sweetpotato Seed Growers Association works closely with
them to supply the sweetpotato industry with quality seed. Field and
storage inspections assure that your seed stock will have:
- Varietal purity
- A minimum of mutations
- Little or no serious disease problems
In most years, it is not possible to buy sufficient certified seed
stock to grow your entire sweetpotato crop. Therefore, you need to
develop and maintain your own seed program and integrate this into
your commercial production program.
- Always use N.C. certified seed stock.
- Fill one-tenth of your total annual commercial seed stock
needs with certified seed stock.
- Increase this certified seed stock for the following year's
- Keep your seed operations separate from your commercial
PRECAUTIONS AND RECOMMENDATIONS
- Handle seed stock (for production of next year's crop)
separately from seed stock for the commercial crop.
- Presprout seed stock. Raise the temperature in the storage
house where seed sweetpotatoes are to 75 to 85oF with
90 to 95% relative humidity for about 3 to 4 weeks. Provide some
ventilation. Presprouting results in earlier plant production and
2 to 3 times more transplants.
- Bed site selection.
- Locate on well-drained soil.
- Rotate plant beds so that sweetpotatoes are not bedded on
the same site for at least 3 years.
- Locate near an adequate source of water for timely
- Fertilize plant beds with a complete fertilizer.
- Soil temperature at 4 inches should be 65oF for
several consecutive days prior to bedding.
- Handle seed stock carefully to minimize skinning and
- Before covering with soil, remove any mutations as well as
off-colored or diseased roots.
- Treat with Botran and Mertect according to label
- Cover with loose soil to a uniform depth of about 2 inches.
Bedding too deeply can result in rotting due to suffocation,
reduced transplant production and later transplant production.
- Treat beds with an approved herbicide to control weeds and
- Cover beds with clear or black plastic mulch immediately
after bedding to warm the soil and speed plant emergence. Punch
a few holes in the plastic for ventilation.
- Cut transplants from the beds.
- By cutting plants rather than pulling, the spread of
diseases from the plant bed to the field is reduced.
- Always cut upward, and never let the knife touch the soil.
- Sterilize the knife frequently by dipping in a 1:1 solution
of chlorine bleach and water.
- Use only new or fungicide-treated boxes for transplants.
- Destroy bedded seed stock when you've finished harvesting
transplants, by herbicide application, disking, etc.
- Occasionally, "mother" roots may look good enough to
- Don't be tempted to sell "used seed stock" on the fresh
market or for processing.
- Bedded seed stock may have been exposed to materials and
conditions that render it unsuitable, even dangerous, for human
- Select fields with well-drained soils and build high ridges
as further insurance against flooding damage.
- Wash all soil from transplanters and other equipment
between use in commercial fields and the seed production fields
to minimize possible contamination.
- Use vine cuttings from certified seed to increase seed
stock for next year.
- Harvesting sweetpotatoes.
- Harvest early to minimize the risk of losses due to cold
and wet conditions later in the season.
- Wash all soil from harvesters and other equipment between
use in commercial fields and the seed fields.
- Use only new or fungicide-treated boxes for seed.
- Cure seed sweetpotatoes at 85oF and 90 to 95%
relative humidity for 4 to 7 days to help minimize potential
losses in storage. Curing should begin as soon after harvest as
- After cutting store seed stock at 55oF and 85%
relative humidity. Separate from commercial sweetpotatoes, in
another building, if possible, to avoid contamination.
- Sanitation! Clean up (remove all sweetpotatoes), and
fumigate seed storage areas during hot summer weather before
For more information please refer to Growing and Marketing
Quality Sweetpotatoes, North Carolina Agricultural Extension
Service Bulletin No. AG-09, 1989, by L. George Wilson and Charles W.
Averre. This publication can be purchased for $2.00 from: Department
of Agricultural Communications, North Carolina State University, P.O.
Box 7603, Raleigh, N.C. 27695-7609.
Always use pesticides according to label directions. The use
of trade names does not imply endorsement of the product named nor
criticism of similar ones not mentioned
North Carolina Cooperative Extension Service
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