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Cover Crop Planting Advisory Maps for Ontario Growers

Planting cover crops during the appropriate time in the fall allow enough time for the cover crops to grow well before killing frost (-4°C) occurs. Late planting causes poor establishment of the cover crops and lower biomass production, and therefore may have less economic return. Temperature is a key factor influencing the cover crop growth, therefore, sufficient thermal accumulation (degree days) are required for successful establishment of cover crops in fields. With the support from Grain Farmers of Ontario, Weather INnovations have been producing and deploying growing degree day (GDD)-based maps in Ontario to advise optimum planting times in the fall for six cover crops: (i) Cereal rye, (ii) Oat, (iii) Radish, (iv) Forage pea, (v) Hairy vetch, and (vi) Buckwheat. For all cover crops, planting can also be done before optimum dates shown in maps.

Please click each cover crop map to see the enlarged view.


(i) Cereal rye (Secale cereal L.):
Cereal rye is a winter annual grass. It can grow in light to heavy soils. It has dense fibrous root systems penetrating deeply in the soil and therefore minimizes the soil erosion and conserves soil moisture. Winter cereal rye also takes up residual fertilizer and manure nitrogen in the fall and reduces leaching. Additional information on cereal rye can be also obtained at


(ii) Oat (Avena sativa L.):
Oat is a fast growing annual grass. The crop is suitable for weed suppression and also suitable for forage and good for erosion control. The crops require less nitrogen than rye. The crop prefers low pH (5.0 to 6.5), but can't tolerate winterkill. Additional information on oats can also obtained at


(iii) Radish (Raphanus sativus.):
Radish is broadleaf short season cover crop. The crop grow well in loam to clay loam soils. It is tolerant to early frost and mild freezing. The crop is a good fit with fall manure application or when excess nitrogen is present in the soil. It is very suitable to suppress some soil borne fungal and nematode diseases as well as weeds due to presence of high glucosinolates. However, it is not recommended in the areas where club root disease and cabbage root maggot are problematic. Additional information can be also obtained at


(iv) Forage Pea (Pisum sativum L):
Forage pea is an annual legume. The crop can grow better in well-drained loamy to clay soil. It prefers cool temperatures and can tolerate freezing temperatures; however it cannot overwinter. Since the root system is shallow, field peas cannot grow well in poorly drained soil. The crop is an excellent nitrogen fixing plant and can add up to 100 Ib/acre of nitrogen in soil. Additional information can be also obtained at


(v) Hairy vetch (Vicia villosa):
Hairy vetch is an annual winter legume and has a vine like growth habit. It can tolerate extreme cold in winter. It can be grown in most types of well drained soil. It fixes nitrogen from air and can provide nitrogen for the next crops. Hairy vetch is a good cover crop if high-nitrogen demanding crops, such as corn will be planted as a succeeding crop. Additional information on hairy vetch can be also obtained at


(vi) Buckwheat (Fagopyrum esculentum):
Buckwheat is a broadleaf short season cover crop. The crop can be planted in a wide range of soil types. Buckwheat is a very good cover crop to suppress weeds, conserve the soil, and attract pollinators as well as plant pests. It is the fastest growing cover crop and provides good ground coverage within a few weeks. Buckwheat is easily killed by frost. It should be killed within 7-10 days of flowering; otherwise volunteer buckwheat will be a problem. Additional information on buckwheat can be also obtained at

Acknowledgement: We thank the Grain Farmers of Ontario for funding support of this project. We also thank University of Guelph, Ridgetown Campus and Ontario Ministry of Agriculture, Food and Rural Affairs for their collaboration in the project.

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