How to Grow Tomatoes on the Canadian Prairies: A Beginners Guide

Growing tomatoes on the Canadian prairies can be a rewarding challenge, but it’s very achievable with the right knowledge and care. The prairie climate is characterized by cold winters, short growing seasons, and sometimes extreme weather, so taking a few important steps can help ensure success. 

Choose the Right Tomato Variety

Select tomato varieties that are well-suited for short growing seasons. Look for early-maturing varieties that can ripen in 60 to 80 days. Some great options and some of my personal favourites and successes include (I have included direct links to these seeds):

• Early Girl: A classic early producer with a shorter growing time https://www.westcoastseeds.com/collections/heirloom-seeds?rfsn=8525446.c2bce3
• Manitoba: Bred for the prairies and with a short growing time https://www.westcoastseeds.com/collections/heirloom-seeds?rfsn=8525446.c2bce3
• Marzito F1: This is a NEW for 2025 hybrid-shaoe and taste like a similar Marzano paste tomato yet small enough for snacking. This tomato is ready in 55 days and can do both snacking and canning. https://www.westcoastseeds.com/products/marzito-f1?rfsn=8525446.c2bce3

 

Start Seeds Indoors

The short growing season in the prairies means you’ll need to start your tomato seeds indoors well before the last frost. Start seeds 6–8 weeks before the last expected frost date (typically late March to early April, depending on your region).

• Soil and Containers: Use a high-quality seed-starting mix, and plant your seeds in small containers or seed trays. Tomatoes need warmth to germinate, so keep them in a warm area (70-80°F or 21-27°C).
• Light: Once seedlings emerge, place them under grow lights or in a sunny south-facing window to provide 12-16 hours of light per day.

Harden Off Seedlings

Before transplanting your seedlings outside, gradually acclimate them to outdoor conditions over a week to 10 days. This process is called hardening off.

• Start by placing the plants outdoors in a sheltered, shady spot for a few hours each day. Gradually increase their exposure to sunlight and outdoor temperatures.

Prepare the Garden Bed

Tomatoes thrive in well-drained, nutrient-rich soil. Choose a sunny spot that receives at least 6 hours of direct sunlight per day.

• Soil Preparation: Work organic matter such as compost or aged manure into the soil to improve texture and fertility. Tomatoes prefer slightly acidic soil with a pH between 6.0 and 6.8.
• Raised Beds or Containers: If your garden soil is heavy clay or poorly drained, consider growing tomatoes in raised beds or large containers to ensure good drainage.

Transplanting Outdoors

Wait until the risk of frost has passed and nighttime temperatures are consistently above 10°C (50°F) before transplanting your tomatoes. This typically happens in late May to early June on the prairies.

• Spacing: Plant tomatoes about 18-24 inches apart in rows that are 36 inches apart to allow good air circulation.
• Deep Planting: When transplanting, bury the seedlings deeply (up to their first set of leaves). Tomatoes can grow roots along their stems, which strengthens the plant.

6Watering and Mulching

• Consistent Watering: Tomatoes need consistent moisture, especially during dry spells. Water deeply, but avoid overhead watering to reduce the risk of diseases. Aim for 1-2 inches of water per week.
• Mulch: Apply a 2-3 inch layer of mulch around the base of the plants to retain moisture, regulate soil temperature, and suppress weeds. Organic mulches like straw or grass clippings work well.

Support the Plants

Tomatoes benefit from support as they grow. Use stakes, cages, or trellises to keep the plants upright and prevent sprawling on the ground.

• For determinate (bushy) varieties, cages or short stakes are usually sufficient.
• For indeterminate (vining) varieties, taller stakes or a trellis system are ideal for supporting the plants as they grow tall.

Fertilizing

• Fertilizing Frequency: Use a balanced fertilizer to feed your tomatoes every 2–3 weeks throughout the growing season. You can also use slow-release fertilizers at planting time to ensure a steady supply of nutrients.
• Avoid Excessive Nitrogen: Too much nitrogen can lead to excessive leaf growth at the expense of fruit production. Focus on fertilizers with higher levels of phosphorus and potassium as tomatoes mature.

West Coast Seeds has a variety of mulches and fertilizers available here: https://www.westcoastseeds.com/?rfsn=8525446.c2bce3

Pest and Disease Management

The prairies have unique challenges in terms of pests and diseases, but you can manage them with these tips:

• Watch for Aphids, Tomato Hornworms, and Slugs: Regularly inspect your plants for pests and remove them by hand or use organic pest control methods, like insecticidal soap or diatomaceous earth.
• Blossom End Rot: This common issue can be prevented by ensuring consistent watering and maintaining proper soil calcium levels.
• Fungal Diseases: Tomatoes are susceptible to diseases like blight. Use disease-resistant varieties, space plants adequately for airflow, and avoid overhead watering.

10. Harvesting

Tomatoes should be harvested when they are fully ripe, which depends on the variety. On the prairies, the growing season can be shorter, so it’s a good idea to pick tomatoes slightly early if frost threatens, allowing them to ripen indoors in a warm, sunny location.

Extend the Season

• Row Covers: Use row covers or plastic tunnels to extend your growing season, particularly for late-season crops. This will help protect your plants from early frosts.
• Indoor Ripening: If a frost threatens before all your tomatoes are ripe, you can pick them green and let them ripen indoors. They will continue to mature, but the flavor may differ slightly.

Conclusion

Growing tomatoes on the Canadian prairies requires planning and care, especially due to the short growing season and unpredictable weather. By choosing the right varieties, starting seeds indoors, and providing proper care throughout the season, you can enjoy a delicious harvest of fresh tomatoes even in this challenging environment! 

 

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