Ontario · Growing Zone 6a
Gardeners in Cobourg, ON can expect the average last spring frost around April 25, and the first fall frost around October 22, based on historical Environment Canada frost data for the area. That gives Cobourg a frost-free growing season of roughly 180 days. Actual frost dates shift by a week or two year to year, so use this as a planning baseline rather than an exact guarantee, and always check your local forecast before moving tender plants outside.
You have your Cobourg frost dates. Now put them to work: GrowBlock counts back your indoor seed-starting weeks, marks your safe planting day, warns you before a frost, and lays your whole season out on one timeline.
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Most warm-season crops (tomatoes, peppers, squash) need transplanting only after the last frost has passed, and are usually started indoors 6 to 8 weeks before that date. Cold-hardy crops (peas, lettuce, spinach) can often go in the ground a few weeks before the last frost. As Cobourg's first fall frost approaches in October, it's time to plan the last harvests for anything frost-sensitive still in the ground.
Approximate dates for common crops in Cobourg, worked out from the local last frost around April 25. Warm crops go out after frost, cold-hardy crops a few weeks before it, and anything with an indoor start is counted back from its sow date.
| Crop | Start indoors | Sow / transplant out | Approx. harvest |
|---|---|---|---|
| 🍅 Tomato | March 21 | May 9 | July 28 |
| 🌶️ Pepper | March 7 | May 9 | July 23 |
| 🥒 Cucumber | — | May 2 | June 29 |
| 🥬 Zucchini | — | May 2 | June 21 |
| 🥬 Lettuce | — | April 4 | May 19 |
| 🥬 Spinach | — | April 4 | May 22 |
| 🫛 Peas | — | April 4 | June 5 |
| 🥕 Carrots | — | April 4 | June 11 |
| 🫘 Bush beans | — | April 25 | June 14 |
| 🥬 Kale | March 7 | April 4 | May 29 |
Guideline dates from Cobourg's average frost window, not a guarantee. GrowBlock tunes these to each variety you plant and adjusts as you build your beds.
This calendar is a starting point. In GrowBlock every date is tuned to the exact varieties you plant and updates as you lay out your beds, and you can share the plan with whoever you garden with, changes show up for both of you.
Build your Cobourg garden planAround April 25 on average, though it can vary by a week or two either way depending on the year.
Cobourg is in zone 6a, with a frost-free season of about 180 days.
Now that you have your dates, here is how to put them to work through the season:
More how-to on the GrowBlock gardening blog.
See frost dates for all Canadian cities covered by GrowBlock.