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Ministry of Agriculture, Food and Rural Affairs

Sweet Potatoes

Other Common Names Include: Sweet potato yam, yam.

Latin Name:  Ipomoea batatas

Plant Family: Convolvulaceae

Close Relatives: Bindweed, morning glory, dodder

Uses and Markets: Culinary (e.g. used similar to potatoes, but also in desserts).

Planting sweet potato slips)Sweet potatoes are often cultivated several times in the first 8 weeks after planting to remove weeds and build up the hills. Sweet potato vines typically close over the rows by the end of July.Mowing sweet potato vines prior to harvest

Sweet potato harvestSweet potatoes being curedNewly harvested sweet potatoes

Agronomics
Production Life Cycle in Ontario

Annual

Hardiness Zone

N/A

Special Notes

Although sweet potatoes are often referred to as “yams”, especially in the southern United States, true yams are a separate tropical root vegetable not related to sweet potatoes. Sweet potatoes are ideally suited to 3,000 or more crop heat units and take 95 to 130 days to mature, depending on variety. In Ontario, ‘Beauregard’ and ‘Covington’ are currently the most commonly grown varieties. For more information on sweet potato production refer to the OMAFRA vegetable guides.

Propagation method

Un-rooted vine cuttings (slips).  Most sweet potatoes slips planted in Ontario are purchased directly from slip suppliers/propagators in North Carolina.  Note that there are import requirements associated with importing plant material into Canada – consul the Canadian Food Inspection Agency for more information.

Greenhouse Seeding/Propagation Dates

N/A

Field Seeding Date:

N/A

Field Transplanting Dates

Late May to early June, after all danger of frost has passed.

In-row spacing

30-40 cm

Between row spacing

102-112 cm

Optimal Soil temperature at planting

>18°C

Fertility

The recommended rate of nitrogen for the sweet potato variety Beauregard is 50 kg N/ha.  Research and recommendations from outside Ontario do not necessarily apply to Ontario growing conditions. In other areas, sweet potato fertilizer requirements vary with cultivar, with Covington having a much greater demand for nitrogen than Beauregard. Click here for phosphorus and potassium application guidelines and for more information on specialty crop fertility.

Soil type

Sand to sandy-loam. Sweet potatoes can grow in clay loam soils but these soils may not warm up quickly enough under Ontario growing conditions.

Soil pH

4.5-7.5, optimal growth at 5.8-6.2

Special requirements for growth habit

Grow in hills approximately 15 cm high and 40 cm wide. Sweet potatoes are mechanically cultivated several times to warm the soil, control weeds and enhance hill formation to ease digging. This is typically done before extensive vine growth.

Optimal Temperature Range

25-35°C

Temperature sensitivity

Cold sensitive below 10°C.

Irrigation requirements

Irrigation beneficial under normal Ontario conditions.

Days to harvest

100-130 days

Specialized equipment

Bed former; modified potato digger.

Harvest
Harvest Scheduling

Single harvest

Hand harvest or machine harvest

Machine harvest

Quality parameters/grades

No established Canadian grades.  U.S. grades  can be used as a general guide, however retailers vary in size requirements.  Always check with your buyer for specific grading requirements prior to packing.

Additional Harvest Notes

In Ontario, the sweet potato harvest generally starts in early September and continues through October.  Mow and side-cut the surface vine growth 1-7 days before the scheduled harvest. Take care not to wound the tender skin of the sweet potato. Chilling injury (exposure of roots to temperatures below 10°C) can greatly increase root susceptibility to decay in storage. Harvest before soil temperatures drop below 10oC for prolonged periods. Transfer roots from the field to curing facilities as soon as possible after harvest.

Post harvest
Special handling/curing

Sweet potatoes require curing immediately after harvest. During curing, maintain temperatures of 26-29°C and relative humidity of 85-95% for 3-7 days. Adequate ventilation and air circulation in the curing facility is critical. Curing should stop once sprouts begin to form. Move into long-term storage after curing. While tobacco kilns and other buildings are sometimes used in the initial years of production, specialized curing/storage facilities will generally be required for larger scale production and long term (more than a few months) storage of sweet potatoes.  

Storage Conditions

Relative humidity (RH): 85-90%

Temperature: 13-16°C

Air Exchange: N/A

Duration: 3-12 months

Pests
Specific pests observed on this crop in Ontario (observations based on limited experience with this crop)

Insects and Invertebrates: White grubs, wireworms, millipedes, aphids, potato flea beetle, mites, golden tortoise beetle, spotted cucumber beetle larvae, aphids, leafhoppers, mites (greenhouse slip production), whiteflies (greenhouse slip production), cutworms (at transplant and post-harvest)

Diseases: Stem rot, scurf (Monilochaetes infuscans), sweet potato feathery mottle virus, northern root knot nematode. Post-harvest storage rots:  Fusarium surface rot (Fusarium oxysporum), Fusarium root and stem rot (Fusarium solani), Rhizopus soft rot (Rhizopus nigricans), bacterial soft rot

Other: Rodents, deer, growth cracks (due to uneven growing conditions)

Other Potential Pests: The following pests have not been observed on this crop in Ontario. However, they are either significant concerns for closely related plants in Ontario, or are reported on this crop in other production areas. This is not a comprehensive list of all potential pests. Not all of these pests will necessarily survive Ontario’s climate, but could potentially survive in a protected environment (e.g. greenhouse, storage facility).

Insects and Invertebrates: Sweet potato weevil*, whitefringed beetle, sweet potato flea beetle, giant sweet potato bug, clearwing moth, armyworms

Diseases: Black rot (Ceratocystis fimbriata), ring rot (Pythium spp.), circular spot/southern blight (Sclerotium rolfsii), Streptomyces root rot/Pox (Streptomyces ipomoea),  dry rot (Diaporthe phaseolorum), Fusarium wilt (Fusarium oxysporum batatas),  southern root knot nematode, reniform nematode, other storage rots (e.g. java black rot, dry rot, punky rot), various viruses (e.g. sweet potato chlorotic stunt virus, sweet potato latent virus, sweet potato leaf curl virus, many others)

Other:

*Indicates pests commonly mentioned as causing significant damage or economic loss to this crop in other regions.

Comments

To date the following pests have been the most significant in Ontario: white grubs, wireworms, post-harvest storage rots.  Viruses can accumulate over time in sweet potatoes and greatly reduce yields - to minimize this, use certified virus-free slips and do not save roots for slip production for more than 2 generations.  Avoiding chilling during harvest, proper curing and maintenance of adequate storage temperature and humidity is important in preventing losses to post harvest diseases.  To avoid build-up of certain damaging soil pests, always allow 2 or more years between sweet potatoes in a field and do not rotate to crops favoured by wireworms (e.g. corn).

This crop is in Crop Group 1: Root and Tuber Vegetables Group, subgroup 1C: Tuberous and Corm Vegetables Subgroup and subgroup 1D: Tuberous and Corm Vegetables (Except Potato) Subgroup. For more information on Crop Groups, refer to the Pest section.  Always refer to product labels, and follow all directions specified on the label, before applying any pest control product.  For more information, consult an OMAFRA specialist. For pest control products registered on this crop refer to OMAFRA Publication 838.

Typical grub damage to sweet potato rootWireworm emerging from sweet potato feeding holeGolden tortoise beetle feeding on sweet potato leafScurf on sweet potato skin

Fusarium rot on sweet potatoesRhizopus soft rot on sweet potatoes

Additional Notes

None

Ontario Research Projects Used to Create This Profile
  1. Bakker, C. and M. Filotas. 2010-2012.  Effect of harvest date on chilling injury and yield of sweet potatoes in Ontario.  Vegetable and Non-Traditional Crops Research Report, Simcoe Research Station, University of Guelph, unpublished.
  2. Bakker, C. and M. Filotas. 2011.  Effect of row cover on sweet potato harvest and yield in Ontario.  Vegetable and Non-Traditional Crops Research Report, Simcoe Research Station, University of Guelph, unpublished.
  3. Bakker, C.,  Filotas, M. and M.R. McDonald. 2011-2012. Sweet potato variety trial.  Vegetable and Non-Traditional Crops Research Report, Simcoe Research Station, University of Guelph, unpublished.
  4. Collin, G.H. 1961.  Sweet Potato production in southern Ontario.  Report of the Horticulture Experiment Station and Products Laboratory.  Ontario Department of Agriculture. 
  5. Eatock, H., Trueman, C., Paibomesai, M. and M. Filotas. 2012.  Diagnosing pest injury in Ontario root crops. Undergraduate Student Experiential Learning Program Final Report, unpublished.
  6. Filotas, M. and J. Allen. 2009.  Development of recommendations for monitoring soil arthropods in Ontario.  Horticulture Crops Ontario Final Report, unpublished.
  7. Filotas, M. and J. Deveau.  2011.  Identifying effective methods for controlling grubs in sweet potatoes.  Horticulture Crops Ontario Final Report, unpublished.
  8. Filotas, M. and J. Deveau. 2012.  Controlling soil arthropods in sweet potato.  Poster for the Ontario Fruit and Vegetable Convention. 
  9. Filotas, M. and C. Kessel.  2010.  Evaluating nitrogen requirements for sweet potatoes in Ontario.  HortMatters vol. 10, issue 7.
  10. Kemp, W.G. and G.H. Collin.  1976.  Feathery mottle virus of sweet potato in Ontario.  Canadian Plant Disease Survey 56:  33-34.
  11. Kessel, C. and M. Filotas.  2010.   Starter fertilizers in sweet potatoes, Ipomoea batatas.  Horticulture Crops Ontario Project Final Report, unpublished.
  12. McKeown, A. and C. Bakker.  1997-2003, 2005. Sweet potato variety trial.  Vegetable and Non-Traditional Crops Research Report, Simcoe Research Station, University of Guelph, unpublished.
  13. McKeown, A. and C. Bakker. 2001. Evaluation of pre-rooting slips.   Vegetable and Non-Traditional Crops Research Report, Simcoe Research Station, University of Guelph, unpublished.
  14. McKeown, A. and C. Bakker. 2000.  Sweet potato cultural trials.  .   Vegetable and Non-Traditional Crops Research Report, Simcoe Research Station, University of Guelph, unpublished.
  15. McKeown, A., Filotas, M. and C. Bakker. 2009-2010. Sweet potato variety trial.  Vegetable and Non-Traditional Crops Research Report, Simcoe Research Station, University of Guelph, unpublished.
  16. Reynolds, L.B., Rosa, N. and A. W. McKeown.  1994.  Effects of harvest data on certain chemical and physical characteristics of sweet potato grown in southwestern Ontario.  Canadian Journal of Plant Sicence 74:  603-606.
  17. Rosa, N., Reynolds, L.B., McKeown, A., Lougheed, E.C., Yada, R.Y., Murr, D.P. and R. Coffin.  1991.  A production, curing, storage and utilization profile for sweet potatoes in Ontario.  Agriculture Canada/Tobacco Diversification Plan - Alternate Enterprise Initiative Program Report.
  18. Smith, I.D.W. and G.H. Collin.  1961.  Sweet potato flower induction.  Report of the Horticultural Experiment Station and Horticulture Production Lab.  Vineland, unpublished.
  19. Sears, M.K., Hallett, R.H., Allen, J. and M. Filotas. 2007.  Elucidating the role of soil arthropods in vegetable agroecosystems and factors contributing to their occurrence as pests.  Canada-Ontario Research and Development Program Final Project Report. 
  20. Westerveld, S.M., C.J. Bakker, and A.W. McKeown. 2007-2008. Determination of nitrogen fertilizer requirements for sweet potatoes. Vegetable and Non-Traditional Crops Research Report, Simcoe Research Station, University of Guelph, unpublished.
References
  1. Ames, T., N.E.J.M. Smit, A.R. Braun, J.N. O’Sullivan and L.G. Skoglund. 1997. Sweetpotato: major pests, diseases, and nutritional disorders. International Potato Centre, Lima, Peru.
  2. Loebenstein, G. and G. Thottlappily.  2009.  The Sweetpotato.  Springer. 
  3. Munro, D.B. and E. Small. 1997. Vegetables of Canada. NRC Research Press, Ottawa.
  4. Ontario Ministry of Agriculture, Food and Rural Affairs.  2010.  Publication 363 Vegetable Production Recommendations 2010-2011.  Queen’s Printer for Ontario, Toronto.
  5. Reynolds, L.B., N. Rosa and A. W. McKeown.  1990.  Sweet potato production guide. Ontario Ministry of Agriculture, Food and Rural Affairs 90-100.  
  6. Zehnder, G. 1998. A sweet potato grower’s guide to insect pest management. Alabama Cooperative Extension System, ANR-1104.