Starting vegetable seeds indoors is a great way to get a jumpstart on the growing season, especially in Ontario’s climate, where winters can be long and spring can take time to warm up. Knowing when to start your seeds indoors depends on the type of vegetable you are growing and your local frost dates. Here’s a guide to help you plan your indoor seed starting schedule in Ontario.

Understanding Ontario’s Growing Season

Ontario falls into various plant hardiness zones, ranging from Zone 3 in the north to Zone 7 in the south. The last frost date in southern Ontario (Toronto, Hamilton, and Windsor regions) is typically between late April and mid-May, while in northern areas, it can be as late as early June. The key to successful indoor seed starting is counting backward from the expected last frost date.

When to Start Seeds Indoors

Here are some common vegetables and their recommended indoor planting times:

January to February:

Onions, leeks, and celery (10-12 weeks before transplanting)

March:

Peppers, eggplants, and tomatoes (6-8 weeks before transplanting)
Broccoli, cauliflower, and cabbage (6-8 weeks before transplanting)

April:

Cucumbers, melons, and squash (3-4 weeks before transplanting)
Herbs like basil and parsley (4-6 weeks before transplanting)

May (Just Before Outdoor Planting):

Beans, peas, and corn (can often be directly sown outdoors in late May or early June)

Tips for Successful Indoor Seeding

Use High-Quality Seed Starting Mix – This ensures good drainage and aeration.
Provide Adequate Light – A south-facing window may not be enough; consider using grow lights for 12-16 hours a day.
Keep Soil Moist but Not Soggy – Use a spray bottle to keep the soil damp without overwatering.
Maintain Proper Temperature – Most seeds germinate best at 18-24°C (65-75°F).

Harden Off Your Seedlings – Gradually introduce them to outdoor conditions before transplanting by placing them outside for a few hours a day over a week.